Here's the 2013 Colorado Rockies in a nutshell: Tulowitzki, Gonzalez, Fowler, Rosario, the decaying corpse of Todd Helton, and a random sample of pitchers that may or may not struggle in 2013 and beyond. It's a pretty solid core of players, but there are still plenty of question marks on the team.
My x-factor for the Colorado Rockies in 2013 in Drew Pomeranz.
Pomeranz was the crown jewel of the Ubaldo Jimenez trade with the Indians from 2011. The former fifth overall pick in the 2010 draft out of Ole Miss, Pomeranz was traded after just 18 starts in the Indians organization. The Rockies have been aggressive with him, and Pomeranz made 22 starts in the majors last season along with nine starts in AAA.
In AAA, Pomeranz has pretty good, but still needed work. He struck out nearly a batter per inning, but still walked nearly four hitters per nine. In the majors, both his strikeouts and walks went in the wrong direction, and his homer rate absolutely went through the roof. His flyball rate was a little higher than the league average, and his HR/FB was also a little high, two factors that could doom his success at the major league level if he doesn't get them under control, especially playing his home games at Coors Field.
Then again, getting his walks in order is probably the prime concern for Pomeranz going forward. Plenty of pitchers have a high flyball rate and are still able to thrive (with Jake Peavy, Matt Moore, and Jered Weaver sitting as just three examples from a year ago), but not many pitchers are able to thrive with a 1.80 strikeout to walk ratio. Pomeranz is a blue chip talent for the Rockies, and if he's able to put together a solid season in 2013, their rotation will be in much better shape than if he struggles.