From ESPN:
The Arizona Diamondbacks have a solid farm system, but most of their top talents are at least two or three years from cracking the majors. The lone exception is right-hander Jarrod Parker, who is coming off a missed season due to Tommy John surgery on throwing elbow. The 22-year-old is fully healthy and could break into the big leagues this season, writes Bob Baum.
Parker has top-of-the-rotation stuff, having fanned 212 batters in 215 minor league frames, and issued just 71 walks. There's little doubt he can get outs for the D-backs this season, but how early may depend on the club's restrictions for their prized arm.
Parker's career high is the 117 2/3 innings he threw in his first pro season in 2008, suggesting that his workload may be severely abbreviated this season. Such a limit likely means he starts the season in the minors and rises to the majors sometime after the organization feels secure on two issues: One, that Parker's arm is fine and the work he;ll receive in the major leagues will not hurt the pitcher or the team; and two, that the service time threshold has passed so the club doesn't have to worry about Parker becoming arbitration eligible before he has three years under his belt.