The most important move in NFC West

The St. Louis Rams signed Jake Long and had two first-round NFL draft choices this year. The Seattle Seahawks added Percy Harvin, Cliff Avril and Michael Bennett. The San Francisco 49ers added Anquan Boldin and three of the first 55 players selected in the draft.

2012 QB Comparison

None of those moves is likely to affect the won-lost column as much as a trade costing a conditional 2014 seventh-round pick and a swap of 2013 late-round choices.

The Arizona Cardinals' deal for Carson Palmer should equate to nearly four additional victories in 2013 if Palmer plays near the same level he played with the Oakland Raiders last season. And if Palmer enjoys a career revival playing with Larry Fitzgerald, the expected total would increase.

There is no way to know for certain how many games a team will win, of course. But the brains behind ESPN's Total QBR metric do know that a quarterback with, say, a 65.0 QBR score in a single game will have close to a 65 percent chance of winning. That has been established over the past five seasons.

To calculate the difference in expected victories for Arizona with and without Palmer, we first must know the average single-game 2012 QBR scores for Palmer and for the Cardinals' quarterbacks. The average was 44.2 for Palmer and 20.5 for the Cardinals.

The difference in expected winning percentage is 23.7 points (44.2 minus 20.5). That works out to 3.8 victories over a 16-game schedule.

Arizona has made many changes this offseason, so it's not like we can simply add 3.8 victories to their total from last season. The team will play a different schedule. The team will have new schemes with new personnel.

In the end, though, we might expect the Cardinals to win about four more games with Palmer than they would have won with a repeat of the 2012 season at quarterback -- whatever their final victory total might be.

It's tough to envision any other NFC West newcomer having a similar impact. Such is the nature of the quarterback position, and such is the gap between what the Cardinals got from their quarterbacks last season and what they're likely to get from Palmer.

Note: The chart shows cumulative season QBR scores. Those are usually the most useful ones, but we needed per-game averages to calculate a victory differential. Thanks to Jason Vida and Alok Pattani of ESPN Stats & Information for their help with this item.