No. 2 Roy Halladay, Philadelphia Phillies
The Phillies made a return trip to the World Series last season. If GM Ruben Amaro had not landed pitcher Cliff Lee at the trade deadline though, they may not have even advanced past the first round of the playoffs or made the postseason tournament.
Lee gave them the much needed bona fide No. 1 starter that was otherwise missing when Cole Hamels lost his command, stuff and/or mojo during the post championship P.R. tour.
Fast forward to December, 2009. A couple offseason winter deals later— exit Lee, enter Roy Halladay. The latter now holds down the "top of the rotation stud" role in Philly.
Halladay is arguably the best starting pitcher in baseball. And, make no mistake about it— he is critically important to the Phillies lofty aspirations in 2010.
With Hamels continuing to look a lot like last year's edition, rookie phenom J.A. Happ and Joe Blanton logging lots of time on the D.L., and a 47-year old pitcher completing the rotation— handing the ball to a classic stopper like Halladay every fifth day has kept them in first place.
The lanky right-hander has started with a flourish, going 6-1 with a 1.45 ERA. No real surprise for a perennial top-five Cy Young finisher with a 154-77 career record and 2.78 ERA over the past two years.
With him, the Phillies are a legitimate championship contender. Without him, not so much.