One of the recurring themes I had to deal with in evaluating rosters for our season previews was how to define an ace. Additionally, as I was watching Justin Verlander pitch last night I was struck with the notion that while Verlander isn't a poor pitcher by any means, he might not be one of the true 'shut-em-down' aces that teams rely on. Obviously, Verlander is the ace of the Tigers rotation. That being said, being tabbed as a number one starter doesn't necessarily mean you are a good pitcher (Luke Hochevar) or even the best on your team (Ian Kennedy, Mark Buerhle).
If wins were the measure of an ace then Verlander would be in the discussion as he has won 17 or more games in four of his five seasons. Indeed, only Roy Halladay (90) and C.C. Sabathia (88) have won more games since Verlander entered the league. However, if you look at adjusted ERA (ERA+) over that same span for pitchers with more than 600 innings pitched during that period then Verlander slides to 20th in baseball.