Carson Palmer sat. David Carr didn't. Risk Mirer started. Drew Brees didn't. For every highly-drafted rookie quarterback, there is a debate about whether they should get the keys to the offense or the clipboard. Brian Burke at Advanced NFL Stats took a look at quarterback success based on whether or not the quarterback in question sat for a year or played right away. As always with these, click through to view the charts and tables.
The underlying assumptions attempt to account for the potential of a quarterback, as better quarterbacks should have a higher chance of starting earlier as well as a greater chance of long term success. Given that we don't live in Madden, Burke used draft position as an indicator of QB potential. Standard disclaimers about imperfect information apply.
Burke's metric of choice is a tweaked version of Career Adjusted Yards per Attempt. By regressing Career Adj. YPA versus draft position, Burke found a fairly clear downward trend. He then calculated the Career Adj. YPA Above Expected for each QB in the sample.
Depending on your stance on the issue, the result is somewhat surprising:
As it turns out, it appears that QBs with more rookie starts tend to enjoy greater career success, even accounting for draft order.
Some of you might have noticed that what I've really done here is a crude multivariate regression. Holding for draft order, I estimated the effect of games started. What if we just do the regression directly?
As expected we get a small negative effect with draft order. (The higher the pick number, the worse the expected stats.) The Games Started variable is positive and significant at p=0.03. The model as a whole has an r-squared of 0.15--small in absolute terms, but considerable given the highly random individual variance in QB careers.
Even when Burke adjusted the grouping to break at various numbers of games played as a rookie, the results remain the same. Quarterbacks appear to benefit from starting as many games as possible as a rookie.
Given this analysis, there is no reason for a coach to arbitrarily keep a rookie QB on the bench. He should start his best QB, rookie or not, and not worry about incubating him under a ballcap on the sidelines. In the end, it should be the coach's qualitative judgment on the readiness of the player.
As an aside, there are ancillary effects not covered here, such as the potential damage to a career caused by starting too early. For a late round pick like Mike Teel, starting right away could result in such a poor showing that they could play themselves out of the league as a rookie. With lesser investments in late round picks, teams would be less inclined to hang onto someone who showed nothing.