Despite a superficially ugly line (6.12 ERA), Holland actually pitched well for a rookie, posting a 4.38 xFIP last season.
Poor luck on HR/FB rate (14.9%; welcome to Arlington), BABIP (.321), and strand rate (64.7%) made his season look far worse than it actually was.
Holland is more of a strikeout pitcher than Feldman, Hunter, or Lewis, and he's the only lefty in the rotation.
Arlington is a lefty-hitter-friendly park, so lefty pitchers can be expected to get better HR/FB luck there than righties, all other things equal.
Holland's got a decent low-90's fastball and a pair of impressive breaking pitches. He's got three things he needs to work on:
1.) Changeup (it was AWFUL in 2009)
2.) Pitch usage (more breaking stuff, fewer fastballs)
3.) Consistency and command (A given for most young hurlers; he's no exception)
Given his youth, upside, decent rookie year, and relatively short list of needed improvements, Holland has a decent chance of actually being the best starter on the Rangers this year.