Evidence of Momentum: Big Plays Early Create More Wins

Momentum in NFL games is the stuff of legend. Sometimes a key play or drive early is all it takes to put the game out of reach. For example, on September 30, 2012, Atlanta Falcons QB Matt Ryan threw a 49 yard TD pass to WR Roddy White with 33 seconds left in the first quarter. The TD pass felt like a game changer, a big play that would no doubt help them beat the Carolina Panthers. The win put the Falcons at 4-0, which later turned into 8-0 — the best start in franchise1 history. 
Big plays early aren’t always harbingers of success, though. Most of us probably also remember that Devin Hester returned the opening kickoff of Super Bowl XLI 92 yards for a touchdown. Hester’s TD undoubtedly felt like a tone setter, too, but this time the outcome was different — the Bears lost the Super Bowl to the Colts 2917. 

Early Momentum
So do plays like Ryan to White and Hester’s early return TD actually change the game? Do they create momentum? And what role, if any, does momentum play in determining who wins or loses a game?
Logically, it makes sense that these type of plays “set the stage” for the rest of the game, but the results of several studies2 suggest that momentum doesn’t exist in the NFL3.
To examine momentum from a different angle, we looked at a sample of the 1120 games between 2000 and 2012 where only one team had a big play in the first quarter. All things being equal, chance suggests that any given team has a 50% chance of winning any given game. However, when a team makes a big play in the first quarter, that team goes on to win the game 63% of the time, which is a statistically significant increase of 13% over chance.
However, there is a caveat to this result: most of the teams (61%) that completed big plays in the first quarter went on to have winning records overall. So, it could be that winning teams make more big plays than losing teams. To control for this possibility, we split the sample into two groups, which allowed us to see the effect of an early big play on teams with winning and losingrecords independently.
1. Winning teams (above .500 record; 9 or more wins in a season): Overall from 2000 – 2012, these teams averaged 10.82 wins per season, for a winning percentage of 67.6%. On average, teams who finish with 9 wins or more will win any given game 68% of the time.
2. Losing teams (below .500 record; 7 or fewer wins in a season): These teams averaged 5.05 wins per season from 2000 and 2012, a winning percentage of 31.6%. On average, teams who finish with 7 or fewer wins will win any given game only 32% of the time.


The Early Bird wins More Games


Teams with winning records who had a 40+ yard play in the first quarter went on to win the game 76% of the time — good for a statistically significant 4 8% higher winning percentage from their expected winning percentage of 68% going into the game.
On the other hand, teams with losingrecords who completed a 40+ yard play in the first quarter went on to win the game 43% of the time — a statistically significant5 11% higher winning percentage above the 32% winning percentage they would have expected otherwise.
Regardless of a team’s final record, a team that had a 40+ yard play in the first quarter also had about a 10% higher chance of winning. If you’re a head coach: shoot for the fences in the first quarter. And if you’re an overmatched team, definitely scour your playbook for those plays that might get you 40+ yards in the first quarter.

What do you have to lose? The game.

1 http://en.wikipedia.org/wiki/Atlanta_Falcons


2 http://www.sloansportsconference.com/wp-content/uploads/2012/02/92-Big-Plays-and-Psychological-Momentum-in-the-NFL.pdf


3 http://www.advancedfootballanalytics.com/2013/11/momentum-1.html


4 X2 (2, N = 609) = 15.96, p < .01


5 X2 (2, N = 413) = 23.56, p < .01

Comments

  1. When people talk about 'momentum' they typically mean something that isn't captured in the score, down, distance, and time left. So, if you want to test whether early big plays lead to a momentum advantage, then maybe you should be comparing teams that go ahead early with small plays to ones that go ahead early with big ones.

    Plugging some numbers into Brian Burke's calculator (http://wp.advancedfootballanalytics.com/winprobcalc1.php) it seems like there is little to no difference between what you expect for teams that get one early 40 yard play, and ones that string together 40 yards with 12 4-yard gains.

    P.S. It's nice to see references posted, but the links seem to be broken.

  2. Ugh. Did it ever occur to the author that a 40-yard play at *any* time in the game significantly helps that team win? No evidence was presented here that momentum exists — at all.

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