Will new QBs improve teams?

There have been myriad quarterback switches in the NFL so far this season. AP Photo

What's up with all the quarterback switches going on in the NFL? Glad you asked. Since Total Quarterback Rating calculates the points added by every quarterback to his team on every play, we can use its data to estimate the impact of the various QB substitutions, voluntary or otherwise, happening right now.

For each team that has made -- or is making -- a change, I looked at the clutch-weighted expected points added by the incoming and outgoing quarterbacks since the start of the 2009 season. I have ranked the clubs by the difference between the new and old QBs per 35 plays, which is about how many plays a starting quarterback takes part in per game, whether by dropping back to pass or on a QB run. So a score of -1.23, for example, would mean the team stands to lose an average of 1.23 points per game because it's changing QBs. As you'll see, there are several points that require more estimates or conjecture, but this is my best guess about what QBR has to say about the league's new crop of signal-callers.

Denver Broncos (+0.63)

In his very limited action so far, Tim Tebow has scored well in QBR, not just somewhat infamously in Week 5, but also by adding 9.8 expected points to the Broncos' offense in just 143 plays last year. Tebow has so many unusual attributes -- his size, his mobility, his ability to inspire, the fact that he invented cold fusion -- that there's no reliable way to tell how he's going to perform in extended playing time. Aside from fan worship and his willingness to play like a fullback, however, Tebow may have two things working in his favor.

One is that all his moving around may help him avoid sacks. In his relief stint against San Diego, he didn't have any negative-yardage plays. And while he has completed fewer than 50 percent of his passes, when he has connected, it's been for fairly huge receptions -- 16.3 yards per catch in his short career. If Tebow can actually avoid ball-discipline mistakes and throw for big gains while rushing for more than 5 yards a pop, he's going to put points on the board. But nobody's ever succeeded with that mix of skills before, so the only way we're going to find out if Tebow can do it is to watch him play.