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The New York Jets are 5-4 after upsetting the New Orleans Saints at home on Sunday.
Before the season, they were picked as the fifth-worst team in the league by the bookmakers. They traded their best player in Darrelle Revis before the draft and inserted rookie Geno Smith at quarterback.
So at 5-4, they're one of the NFL's biggest surprises.
But there are some red flags around this team.
The biggest red flag is point differential. The Jets have a point differential of -63 right now — the sixth-worst number in the league. In their four losses they've lost by an average of 20.25 points per game. In their five wins they've won by an average of 3.8 points per game.
When you put these point differential statistics into the Pythagorean expectation model — a simple formula invented by Bill James that predicts a team's number of wins based on point differential — you find that the Jets have played worse than their record indicates.
Based on the formula, the Jets' expected wins through the first nine games is ~2.9. So at 5-4, they're currently overachieving by 2.1 wins (or 72%).
As Grantland's Bill Barnwell noted in his breakdown of Pythagorean expectation in 2012, "Point differential is a better indicator of future winning percentage than winning percentage itself."
That's not to say the Jets will definitely collapse in the final seven games.
But right now they have the statistical profile of a 3-6 team, not a 5-4 team. To maintain that record and make the playoffs in the final two months of the year, they'll need to play significantly better.
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