Which NFL team won the QB derby?

Which one of these quarterbacks will help his new team the most this season? US Presswire

This period of free agency is historic in the sense that it's probably the first time in league history that the quarterback fortunes of nearly one-quarter of NFL teams have been affected in such a short span of time.

So, did those teams' fortunes change for the better or the worse? Would they have been better off letting a rookie QB play instead of using a veteran QB as a stopgap measure?

Let's take a metric look at some of the biggest impact moves to find out.

Arizona Cardinals -- Traded with Philadelphia to acquire Kevin Kolb

This might sound harsh, but Kolb's numbers from last year's don't exactly say he is a slam dunk improvement over Derek Anderson. Kolb's 6.2 overall yards per attempt (YPA) mark was the third lowest among quarterbacks with 175 or more pass attempts. (Note: The YPA totals throughout this article include penalty plays such as pass interference, illegal contact, etc.) He also fared quite poorly in the bad decision metric (a bad decision being defined as when a quarterback makes a mistake with the ball that leads to a turnover or a near turnover). His 4.0 percent showing in that category ranked tied for third highest in the league.