Why are the New York Jets and Miami Dolphins doing so much better this year compared to last? Their new quarterbacks are immediately credited, but are they the real reason? What about the defense and the running game? And how does Favre's passing numbers compare to the Jets of last year? Are they really any better than those of the Chad Pennington/Kellen Clemens duo from 2007? I'll break down each facet of the game and tell you where each team's improvements have really come from.
The first consideration is strength of schedule. Last season both the Jets and Dolphins faced a tougher than average schedule. With division bully New England finishing the regular season 17-0, each team's opponent average win probability was 0.55. In other words, their opponents averaged a 55% expected winning percentage. That puts both teams in the top 5 in terms of schedule difficulty for 2007.
This year is quite different. The Dolphins opponent average win probability is 0.50, perfectly neutral, meaning their opponents have been league-average in terms of difficulty. The Jets, however, have faced a relatively easier schedule. Their opponents average 0.43 in expected win probability. So both teams can thank an easier schedule so far this year, the Jets more than the Dolphins.
But opponent strength only tells part of the story. Both the Jets and Dolphins have fundamentally improved, most prominently in their offensive passing games. Most analysts will point to total yards or touchdowns scored, but we know those stats can be very misleading. Let's look at efficiency stats for the real story.
The tables below list each team's efficiency stats for all of 2007 and 2008 through week 10. The year-to-year difference in each stat is also listed. Each facet of the game is not equally important, so the bottom row of each table lists the estimated number of wins a team can expect to improve or decline based on the change in each stat. For example, the improvement in Miami's offensive passing efficiency of +2.2 net yards per attempt would normally result in a gain of 3.3 wins over the course of a full season. These estimates are based on a regression model detailed in this article.
| TEAM | OPASS | ORUN | OINTRATE | OFUMRATE | DPASS | DRUN | DINTRATE | PENRATE |
| MIA '07 | 5.0 | 4.1 | 0.031 | 0.027 | 6.6 | 4.6 | 0.034 | 0.34 |
| MIA '08 | 7.1 | 3.9 | 0.017 | 0.015 | 6.7 | 3.7 | 0.024 | 0.29 |
| Difference | +2.2 | +0.2 | -0.014 | -0.012 | 0.1 | -0.8 | -0.011 | -0.05 |
| Wins +/- | +3.1 | -0.2 | +0.7 | +0.6 | -0.1 | +0.5 | -0.9 | -0.1 |
Miami's passing game is clearly the biggest difference. Between passing efficiency and interception rate, the passing game alone is responsible for a whopping +3.8 gain in wins. Despite all the attention garnered by the Wildcat offense, the Dolphins' running attack is actually slightly worse this year than in 2007. All together, the Miami offense is responsible for an improvement of +4.2 wins.
Overall, their defense is actually slightly worse this year. Although they are stopping the run better, run defense doesn't translate into many wins. They've also been unlucky in the defensive interception department. All together, the Dolphin defense can be credited with half a loss (-0.5 wins).
Now let's look at the Jets.
| TEAM | OPASS | ORUN | OINTRATE | OFUMRATE | DPASS | DRUN | DINTRATE | PENRATE |
| NYJ '07 | 5.4 | 3.7 | 0.039 | 0.020 | 6.6 | 4.2 | 0.035 | 0.24 |
| NYJ '08 | 6.2 | 4.6 | 0.045 | 0.024 | 6.0 | 3.2 | 0.030 | 0.30 |
| Difference | 0.8 | 0.8 | 0.006 | 0.004 | -0.6 | -1.0 | -0.006 | 0.06 |
| Wins +/- | +1.2 | +0.8 | -0.3 | -0.2 | +1.0 | +0.6 | -0.5 | +0.2 |
The Jets' numbers tell a different story. Their improvement this year has come from both the offense and defense. Favre has helped improve the passing game, but he's throwing interceptions at an even higher rate. The Jets' passing attack is responsible for only +0.9 additional wins over last year. The running game has improved just as much, going from a solidly below average 3.7 yards per rush to a solidly above average 4.6 yards per rush. All together the Jets offense can take credit for an improvement of +1.5 wins.
Their defense is also pulling its fair share of the load. Significant improvements in both running and passing efficiency combine for an improvement of +1.5 estimated wins. Their defensive interception rate has declined slightly from 2007, giving back half a win on average. In total, the Jets' improvements have been across the board in contrast to the Dolphins' offensive passing resurgence.
It's hard to compare Favre and Pennington directly. But the one observation I will make is that a 0.045 interception rate is extremely high. That means about 1 in 20 of Favre's passes are intercepted. Favre, with better receivers and arguably better protection, is achieving 6.2 net yards per attempt--essentially league-average--with that very high interception rate. It's hard to see how a team can continue to win giving up that many interceptions.
Pennington, on the other hand, has faced slightly tougher defenses so far and is getting 7.1 net yards per attempt. And he's doing it with a very low 0.017 interception rate. That's about 1 in 60 passes. Plus, his team's running game isn't nearly as threatening as the Jets'. But wins are the bottom line, and right now New York has the edge.
Win probabilities for week 12 NFL games are listed below. The probabilities are based on an efficiency win model explained here and here with some modifications. The model considers offensive and defensive efficiency stats including running, passing, sacks, turnover rates, and penalty rates. Team stats are adjusted for previous opponent strength.
CIN at PIT 
CAR at ATL 
BUF at KC 
CHI at STL 
NYJ at TEN 
NE at MIA 
MIN at JAX 
PHI at BAL 
HOU at CLE 
TB at DET 
SF at DAL 
OAK at DEN 
NYG at ARI 
WAS at SEA 
IND at SD 
GB at NO 
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