Comparing quarterback performances

Matt Hasselbeck of the Titans had the best game of AFC South quarterbacks Sunday when measured by the NFL’s passer rating. But according to the alternate metric, QBR, Houston’s Matt Schaub had a better day.

Passer rating maxes out at 158.3; QBR goes to 100.

For a game, QBR can be interpreted as a percentile, so a score of 80 means a QB’s performance was better than 80 percent of all QB games.

Why is Schuab’s QBR so much closer to his passer rating while Haselbeck’s is so different?

I asked ESPN Stats & Info and got this back from Dean Oliver:

“It was a combination of two factors. The first is that Schaub’s performance was in a closer game, whereas Hasselbeck was playing with a substantial lead most of the game. The second is that Schaub was a little better on third downs, which, in combination with the game being close, really elevates his numbers.”