Chase Stuart
Footballguy
http://fifthdown.blogs.nytimes.com/2011/11/15/brees-has-unitass-streak-in-his-sights/
Before the final week of the 2010 regular season, I noted that Drew Brees and Tom Brady had thrown at least one touchdown pass in each of their team’s first 15 games. Brady threw a pair of touchdown passes against Miami in the season finale last season, and has thrown at least one touchdown pass in every game this year, giving him 25 consecutive games with a touchdown pass. But Brees also kept his streak alive in Week 17 last season. In fact, after throwing for two touchdowns against the Falcons on Sunday, Brees has now thrown a touchdown pass in 37 consecutive regular-season games.
Over a five-year period from 1956 to 1960, Johnny Unitas threw a touchdown pass in 47 consecutive games in which he played, a record that has yet to be broken. Unitas missed two games with injury during the streak — and Brees missed one game during his streak when the Saints had already clinched the N.F.C’s top seed and he had set a league record — but missed games are not counted by the N.F.L. for purposes of such touchdown streaks.
Now that Brees is within shouting distance of the record, what’s the likelihood of him actually tying or breaking it? There are many variables that make it difficult to get a precise estimate. But here is how I would look at it.
Brees is throwing for a touchdown on 5.5 percent of his passes this season, consistent with his 5.6 percent average from 2008 to 2010. So let’s assume that over his next 10 games (which will stretch into next season, as only regular-season games are counted by the N.F.L. for such purposes) Brees will be on his same general touchdown pace since 2008.
The Saints consistently averaged around 11 drives per game in each of the past four seasons. In the 57 games Brees has been active during that time, New Orleans has had 619 drives (excluding take-a-knee drives at the end of a half), for an average of 10.9 drives per game. During that time, Brees has thrown 124 touchdown passes, or 0.20 touchdown passes per drive (and 2.18 touchdowns per game).
Since 2008, one in every five Saints drives has ended in a touchdown pass by Brees. If we assume 11 drives in a game, simple math tells us there is a 91.4 percent chance of Brees throwing a touchdown in any given game. But the odds of Brees throwing a touchdown pass in 10 straight games would be only 40.7 percent, and the likelihood of him breaking Unitas’s record by throwing a touchdown in an eleventh game is just 37.2 percent.
We could also use something called a Poisson distribution to estimate Brees’s likelihood of recording a zero-touchdown game. The Poisson distribution is widely used by statisticians because it expresses the probability of a given number of events occurring (zero touchdown passes) in a fixed interval of time (one game) if these events occur with a known average rate (2.18 touchdowns per game) and independently of the time since the last event. Based on the assumption that Brees is a 2.18 touchdown per game player, the Poisson distribution estimates that Brees has an 88.6 percent chance of throwing for a touchdown in any given game. That would indicate that Brees has roughly a 27 percent chance of breaking Unitas’s mark.
Of course, all such analysis assumes several things. One, it assumes that Brees stays healthy. Two, it assumes New Orleans does not change its offensive philosophy to maximize Brees’s odds of setting the record. There is also the assumption that each drive is an independent event, which is not true. Brees may have a 25 percent chance of throwing a touchdown pass on any given drive against a bad pass defense but only a 15 percent chance against an elite pass defense. Brees may simply have an off game, as we saw earlier this year against the Rams (more on that below). In general, the assumption that each drive is an independent event is likely to overstate Brees’s odds of throwing a touchdown pass in any given game. On the game level, note that Brees would need a 94 percent likelihood of throwing a touchdown pass in each game — instead of 91.4 percent — to be more likely than not to throw a touchdown in each of his next 11 games.