However, the part of the story line that’s true is that Romo is a boom-and-bust performer. He can both lead his team to a dramatic victory, as he did last week in Washington, or make bone-headed plays to let victory slip from his team’s hands, as he did the week before in Green Bay.

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Of all the quarterbacks with over a full season worth of pass attempts since 1999, Romo ranks 15th out of 152 qualified players in the game-by-game variance of WPA, which measures how far apart the peaks and valleys in a statistic tend to be.

This isn’t necessarily a good or bad thing, but it does quantify the roller-coaster ride that Dallas fans have been on. (It shouldn’t surprise anyone that Mark Sanchez, Matthew Stafford, Geno Smith, Joe Flacco, Jay Cutler and Robert Griffin III rank in the top 25 of that list.)

Looking ahead to Sunday, the Dallas backup Kyle Orton’s numbers aren’t inspiring. His career WPA per game is exactly zero, meaning his performance has, on net, neither helped nor hurt his teams’ chances of winning.

Estimating the effect of replacing Romo with Orton on Sunday night is much more complicated than simply swapping their career average numbers, but it’s safe to say that Dallas’s actual chances of upsetting the Eagles are about 10 or more percentage points below what is indicated by the efficiency model’s weekly probabilities.