Philly's Inferno

A sports fan’s opinion through the lens of Philadelphia’s seventh circle of hell.

Improvement Ahead – Philadelphia Eagles 2013 Win Probabilities

Originally published May 3, 2013 on

The NFL Draft is over, and while we wait for the OTA’s and mini camps, it’s time to focus on the Philadelphia Eagles’ 2013 schedule.  For a Chip Kelly squad that will want to play fast, the NFL *cough* graciously accommodated.  The Eagles open the season with three games in 11 days, and two of those games are during prime time, so we may know pretty quickly how Kelly’s team responds to high speed and short rest.  Hopefully smoothies help.  But in actuality, how might the team perform next season?

Before the draft, I took a cue from Bill James and used Pythagorean expectation to project the Eagles will win five games in 2013.  However, that did not take into account their opponents, who were unknown at the time.  Now that we know who the opponents are, I applied the same Pythagorean expectation formula to them, and used those results as the basis for simulating the Philadelphia Eagles 2013 season.

The model takes the Pythagorean wins for the Eagles and their opponent each week, randomizes those values within the standard error value (2.6 wins), and applies a random “external factor” value to each team.  I included the external factor value to randomly, and cumulatively, account for things like luck, home vs. away games, day vs. night games, win/loss streaks, weather, game planning, the impact of a certain new head coach, etc.  I ran the simulation 1,000 times, so the external factor value changes for each team in each simulated game.  For each game, the products of the modified Pythagorean wins (based on standard error) and external factor values for each team are compared, and the team with the higher product is awarded a win.  Read more…


Hello Matt Barkley, Goodbye Michael Vick

Originally published April 27, 2013 on

If I am Michael Vick, I am not happy.  If I am Vick, I know I am a veteran, injury-prone quarterback with turnover issues and I know I have to compete for a roster spot.  Not a starting spot, but a roster spot.  I know I have to outperform a younger mini-me who has a head start understanding head coach Chip Kelly’s offense (Dennis Dixon).  I know I have to outperform a young competitor who outplayed me behind the same terrible offensive line (Nick Foles).  And I now know I have to outperform Matt Barkley, a hungry fourth round draft pick from USC with something to prove, who is apparently… ahem… leadership-prone.

Barkley is a surprising pick in more ways than one.  First, he was initially projected to be a first round talent.  Second, he was generally and universally believed to not fit the Eagles offense, whatever that offense may look like.  Third, the Eagles traded up a few spots to get him. Exactly what Howie Roseman and Kelly got was a player high on intangibles and low on risk.  Read more…

Chip Kelly Will Soon Draft His Foundation

Originally published April 21, 2013 on

After leaving the state of Oregon, Chip Kelly traveled three thousand miles to Philadelphia and signed a contract for a new home.  But this home was not new construction.  It wasn’t a Toll Brothers McMansion.  No, it’s been around for a while.  It’s been loved.  The real estate agent called it “charming” and said it had “good bones”, and Chip Kelly liked it a lot. And then he gutted it.

I’m not quite sure whether this scenario applies to the Philadelphia Eagles just yet.  We won’t really know if the roster will be gutted until the start of the 2013 season.  However, with all due respect to the players added during free agency, all reported to be the kinds of players Kelly needs, Kelly’s first NFL Draft is the time during which he can lay the foundation for his new football club.

This will be the time during which his legacy will really begin.  Yes, Howie Roseman will be calling the shots, but Roseman will not be calling the shots alone.  Kelly will collaborate and corroborate with him, as will former San Francisco personnel maestro Tom Gamble.  But make no mistake, since Coach Kelly will be molding and coaching these players, they will very much be his.  Read more…

2013 NFL Draft Prospect Odds for Each Philadelphia Eagles Selection

Originally published April 30, 2013 on

Instead of mocking the draft, let’s simulate it.  Previously, I’ve written how principles of a chaos theory-influenced draft simulation can illustrate just how impossible it is to predict what will happen in the NFL Draft.  Each selection in the draft is dependent on the ones that come before it, so changing any of the previous selections can radically alter any one team’s particular pick at the moment, or in the future.  By many accounts, the Philadelphia Eagles seem likely to draft an offensive tackle in the first round, but exactly how likely?

The simulation model was run 1,000 times and we can glean from it the percent chance any one prospect will be drafted at any position in the draft.  The model itself is based on one big board (ideally I would like to use 32 different ones, but maybe next year), and a random decision to draft based on need or best player available.  Once that decision is determined, which team need and which best player available is also determined randomly (within reason), in order to account for value and reaches.  Envision this simulation as a statistical draft performed within a vacuum, with no trades.  Read more…

Value-Scoring the 2013 NFL Draft

Originally published April 30, 2013 on

The three day NFL Draft event is complete and many analysts have already submitted grades for teams as well as individual selections.  Admittedly, it’s a bit unfair to judge a team’s draft and their respective selections so early, before players have a chance to prove their worth on an NFL football field.   Instead, it may be better to grade the draft based on relative value (although, perhaps no less ambiguous).

Earlier, I created a draft model based on chaos theory principles and ran the simulation 1,000 times.  One of the byproducts of that simulation was an average draft position (ADP) for each player.  My goal was to use these ADPs as a basis for my value determination, but in order to do so I first needed to test whether my ADPs were relevant.  That is, did ADP relate any better to actual draft results than an analyst’s mock draft?  For a comparison, I chose Mike Mayock (I wanted to also use Mel Kiper’s latest mock draft but I’m not an ESPN Insider and couldn’t find it anywhere).  Read more…

Will the Philadelphia Eagles Draft Tavon Austin? Expect the Unexpected

Originally published April 24, 2013 on

During an interview with Mike Missanelli on 97.5 The Fanatic, Sal Paolantonio offered a word of caution to Philadelphia Eagles fans.  He said, “If the two tackles [Luke Joeckel and Eric Fisher] are off the board by the fourth pick, don’t be shocked if the Eagles select wide receiver Tavon Austin.”  Missanelli was appalled and pressed Sal Pal further, but Sal Pal simply responded, “All I’m saying is, don’t be shocked.”  I was driving home from work at the time and nearly swerved off the road.  Could Howie Roseman really have the diminutive West Virginia product that high on his draft board?  It’s the NFL Draft, after all, so expect the unexpected.

My answer to that question, by the way, is no.  At least, not before Chip Kelly was hired.  With a good number of weapons on offense, and a larger number of holes to fill elsewhere, it’s hard to believe Austin was that high on Roseman’s initial board.  So in my opinion the better question to ask, and the question that will be answered Thursday is, “How much did Howie’s big board change after Kelly’s hire?”  It’s an intriguing question because it may provide insight into how Roseman, the Clean-Slated GM, operates in this new regime.  Read more…

In Howard Roseman I Trust

Originally published April 17, 2013 on

I pledge allegiance to Howard Roseman of the Philadelphia Eagles…

Andy Reid and Donovan McNabb are so linked in perpetuity that it may be easy to forget that Reid didn’t engineer the Philadelphia Eagles’ 1999 draft.  While the rookie head coach may have had some input, he did not draft Donovan McNabb, Tom Modrak did.  But my guess is, Big Red was kind of ok with it.  So here we are, an era later, and the Winter of Eagles’ Discontent has come and gone and left quite a mess in its wake.   But winter is no longer coming.  There is another fresh start ahead, a new Spring dawns, and in Howard Roseman I trust.

… And to the Franchise, for which he stands…

If you’ve ever read Outliers by Malcolm Gladwell, you’ll know that in order to be a successful genius, not only to do you need to be an expert at something, but you also need to have a certain amount of luck, to be a victim of some fortunate circumstance that places you in an ideal position for success.  I’m assuming here that Roseman is indeed an expert (be it in talent evaluation, draft preparation, general managing, whatever), in that an expert is defined as someone who devotes at least 10,000 hours to a particular skill (that’s six hours per day for 1,667 days).  And I’m hopeful that this is Roseman’s fortunate circumstance.  Admittedly not many with his background have become general managers of an NFL franchise.  So let’s say he fell into it, but for good reason.  He was persistent, he worked hard, and succeeded at every promoted step along the way.  Even though Jeffrey Lurie has absolved Howie of all responsibility for the 2010 and 2011 draft failures, Roseman had a hand in them and has not impressed.  But there has been improvement, peaking with his hire of Chip Kelly, innovator extraordinaire, as well as with his moves in free agency.  Roseman appears to be a guy that learns from mistakes, adverse to repeating them. Read more…

Chip Kelly Says Nice Things about Vick Because He Has To

Originally published April 11, 2013 on

Former Philadelphia Eagles head coach Buddy Ryan often didn’t say nice things about his players, but that was a different time.  Now, in an age of political correctness, carefully managed and overly sensitive public images, and… well… feelings, tact and media savvy are a little more prevalent than they used to be.

Once upon a time, Philadelphia Inquirer columnist and author Mark Bowden (he of Killing Pablo and Black Hawk Down fame… one of my favorites) wrote an article about Buddy that illustrated this unique brand of “Ryanian” savvy:

When Larry Sullivant saw blood spreading on the back of his hand, he was glad.  It had been a long, hot afternoon scrimmage, and this new coach, a squat tyrant with a flat-top crew cut, had accused him of being a slacker and had been riding him hard. Sullivant jogged off the football field anticipating relief.

Sure enough, the coach inspected the gash and said: “Looks bad. It’ll need doctoring.”

Then he grabbed a handful of dirt, spit on the wound and pressed the dirt over it. “That’ll do you,” the coach said. “Now get back out there.” Read more…

The Belmont Stakes 2013 Interactive Simulation

After running a simulation for the Preakness, here is my attempt at modelling the 2013 Belmont Stakes.  I may modify, so check back for occasional updates.

Click on the image to interact.

Belmont 2013 Simulation

What Contributes to Home Field Advantage in the NFL?

Note: If you would like to jump to the interactive NFL Home Field Advantage infographic, click here.

I will never forget “Fourth and 26”. It was early in the morning when we arrived. The parking lots at Lincoln Financial Field were already filling up and it was brutally cold. My friends and I dressed for it – I wore twelve layers – and we brought plenty of food to grill and plenty of beer to drink. The beer we had to drink quickly, because at eight degrees a layer of ice formed on the surface. More than once I tilted a half- full can to take a sip and nothing followed. It was a cruel joke. Regardless, the twelve layers and amount of beer I drank made taking a leak a torturous endeavor. But in reality, there was no better place I would rather have been than that frozen hell. All because of Freddie’s hands. God bless them.

After Donovan McNabb delivered a hard-thrown wobbler that Freddie Mitchell stopped and secured for that critical first down, the Linc erupted. It’s a sound I will never forget. It was a deafening roar. My buddy and I screamed in disbelief and hugged everyone within, and just out of, reach. The Eagles were losing to Green Bay by three points at the time, and that miracle play gave the Eagles a new set of downs, which McNabb used to get into field goal range. There was not a doubt in my mind that David Akers was going to kick the 37 yard field goal needed to force overtime, and the Eagles were going to win it.

There were other great plays in that game (like Brian Dawkins’ interception of Brett Favre in overtime), but would these plays have happened if the game were played in Green Bay instead? Does this game illustrate the importance of home field advantage? It’s actually a question I didn’t intend to ask. This post was initially going to be about whether Chip Kelly’s offensive success formula can be applied to the NFL. In short, it does. But during my research I noticed that home teams have a decided advantage, so my attention shifted.


Home advantage in sports has been a popular research topic. A quick comparison of home team wins to away team wins will demonstrate that the phenomenon exists. For example, in their 2011 book Scorecasting, economist Toby Moscowitz and Sports Illustrated journalist Jon Wertheim looked at NFL wins from 1966 through 2010 and concluded that home teams win 57.3% of the time. The bigger question, and one they address, is why does home field advantage exist at all?

According to writer Stephen J. Dubner, Moscowitz and Wertheim discounted, through research, many of the popular reasons we think home field is an actual advantage:

When athletes are at home, they don’t seem to hit or pitch better in baseball … or pass better in football. The crowd doesn’t appear to be helping the home team or harming the visitors. We checked ‘the vicissitudes of travel’ off the list. And although scheduling bias against the road team explains some of the home-field advantage, particularly in college sports, it’s irrelevant in many sports.

Instead, Moscowitz and Wertheim adopt a theory proposed by a German economist, Thomas J. Dohmen. Dohmen addressed how decisions are influenced by social factors that often contradict our own best interest by looking at how decisions by referees in Germany’s Bundesliga are affected by the home crowd. He concluded that it’s not the crowd’s impact on the players that matter, but it’s the referees who are subconsciously affected. Dohmen found that German referees award more extra time during games in which the home team is behind by one goal, and more time when the game is tied but the home team is in a good position to score.

Sabermetrician Phil Birnbaum summarized Moscowitz and Wertheim’s adoption of this theory to the NFL, in terms of penalties and instant replay decisions:

In the NFL, “Home teams receive fewer penalties than away teams — about half a penalty less per game — and are charged with fewer yards per penalty. Of course, this does not necessarily mean officials are biased. But when we looked at more crucial situations in the NFL … we found that the penalty bias [increases].”

Away teams have their challenges upheld 37 percent of the time, versus 35 percent for home teams. But when the home team is losing, the visiting team wins 40 percent, versus only 28 percent for the home team. So it looks like the referees favor the home team more when they need it more.


I don’t have data to support replay decisions, but on the surface, my own research seems to support Moscowitz and Wertheim’s suggestion that there may be a penalty bias, however subconsciously. From 2009 to 2011, NFL home teams averaged 6.08 penalties (offense plus defense) per game, while away teams averaged slightly more, 6.18. Offensive penalties were nearly identical, with home teams averaging 3.35 and away teams averaging 3.34 per game. The largest difference in penalties appears on the defense, where away teams average 2.84 penalties per game and home teams average 2.73. In addition, NFL home teams won 434 games (56.5%) by an average score of 23.12 to 20.67. Is this enough to explain home field advantage?

To answer this question, I’m using what I call an offensive efficiency rate (OER). This is not to be confused with the Defense-adjusted Value Over Average (DVOA) that uses to calculate offense efficiency. Instead, my efficiency rate is a bit simpler (if you’re familiar with my work, you may remember that I subscribe to a Gladwellian “less is more” kind of philosophy). I define offensive efficiency as:

(rushes + pass completions) / total offensive plays,

where total offensive plays is the sum of rushes, pass attempts, and offensive penalties.

I calculated OERs for home and away teams for the 768 games in my sample, then performed a logistic regression to determine if OERs could predict game outcomes. The results were very conclusive (p-value <.00001). When the home team has a higher OER, the home team wins 89% of the time. When away teams have a higher OER, away teams win 80% of the time. Since the results were significant, I converted the individual team/game OERs to home and away win probabilities. And this is where I observed something I thought interesting. When both the home and away teams have identical OERs, the home team has a higher win probability. For example, when the OERs are equal to 75%, the home team has a 62.6% chance of winning, while the away team has a 46.2% chance of winning. Is this evidence of home field advantage?

Graph 1 PIHF1

I wasn’t sure so I sought help. I reached out to Phil Birnbaum, the sabermetrician who wrote a great review of Scorecasting and provided some interesting insight into Moscowitz and Wertheim’s findings. He suggested to me that, since home teams win more often, they may rush more often to protect a lead, which would in turn inflate their OERs. Since my data does not include play types per quarter, I randomly removed 100 home wins from my sample so OER averages were weighted the same (334 wins) for both home and away teams. I also decided to control for offensive penalties in order to see if there was still a home field advantage in this “equalized” environment, a relative vacuum. According to these new results, home and away win probabilities are nearly identical:

Graph 2PIHF2

Then, when penalties are included, win probabilities extend slightly in favor of the home team:

Graph 3PIHF3

This graph is interesting because it shows a small away team advantage as OER decreases. However, when including penalties in an equalized environment, there does seem to be a slight home field advantage as OER increases. When both teams have an OER equal to 80%, the home team has an 80.8% chance of winning, while the away team has a 73.4% chance of winning. Since we know what HFA looks like in a controlled, equalized environment, and what it looks like in reality (Graph 1), what about turnovers?

In reality, turnovers are the great equalizer. If the home team has just one less turnover than the away team, then home teams have a decided advantage. When OERs are equal to 75% and away teams have one more turnover than home teams, home teams have a 78.5% chance of winning, while away teams have a 28.5% chance of winning:

Graph 4PIHF4

And when home teams have one more turnover than away teams, home field advantage is all but erased:

Graph 5PIHF5

Of course, there are exceptions. For more team-specific details, below is an infographic on NFL Home Field Advantage. Click on it to interact. I determined HFA by subtracting each team’s average Home Win Probability from their Home Opponent’s Win Probability. The larger the difference, the better the HFA. Using this rubric, the Green Bay Packers had the best home field advantage from 2009-2011, while the Washington Redskins had the worst.



Home field advantage definitely exists. As Moscowitz and Wertheim suggest and my own research illustrates, penalties do seem to have a slight influence. However, I cannot claim that this is caused by subconscious referee bias. I also cannot discount the power of the crowd. The fact that away team defenses average more penalties than home team defenses could indicate a referee bias, or it could indicate an away team defensive player’s reaction to a high pressure social situation (the home crowd).

Also, not quantified here, is the home crowd’s impact on the home defense. As Birnbaum suggests, and I agree, humans evolutionarily have a need to defend their home. In football, this is extremely applicable. My guess is, when the home defense is placed in a high pressure, high emotion, high adrenaline situation, they will more often execute its collective desire than the away team’s offense. In other words, even if both team’s may have the same OER, the home defense, feeding off the energy of the crowd, wanting to defend its home, is more likely to obtain that “key, timely stop” than when playing away. Perhaps this is why Darren Sharper did not defend Freddie Mitchell like he was supposed to. So Eagles fans, continue the deafening roar.

Special thanks to Phil Birnbaum. Check out his work at and