Reed has a fairly typical right-handed reliever profile. He ended up in the bullpen for all the usual reasons. There were concerns about his stamina given his relief profile in college, plus his lack of a legit changeup meant he really didn't have anything to attack lefties with the next few times through the order.
The fastball ran 92-94 in 2013 (down a tick from '12) with very good rising action and relatively little run. The velo/movement combo gets a very high number of whiffs and also leads to a lot of flyballs. He typically commands it well enough when throwing to his favorite spots, but struggles to consistently move it back and forth across the plate. Against all but the most advanced hitters, this isn't a huge problem. The pitch is not, however, something along the lines of Matt Thornton's 2008-10 stretch with his fastball. Reed's heat is legit, but can't quite bear an elite tag. Call it a 65 on the 20-80 scale. And I'd hear arguments for a 70.
The slider, however, remains a work in progress. 2013 represented a step forward, as he used it sparingly the year previous. In '12, he struggled to spin the ball consistently with concomitant location issues. As ever with White Sox pitchers, "Coop'll fix 'im" turned out once again to not be bullshit. After last season, it's fair to call Reed's slider an average offering. He showed improved feel for the pitch and spotted it ably. With additional work, it could become a plus offering, though I'm not sure he'll ever really get the reps or the coaching at this point. Most pitching coaches are not Don Cooper and the D-Backs are buying what they think is a finished product.
His third pitch, the changeup, is fine enough as a show-me pitch. In 2012, it would flash average and surprise batters often enough for decent results. But given the struggles Reed had with the slider, you might think he'd compensate more than he did with the change. Instead he just threw more fastballs.
As mentioned, his command and feel for pitching is good, particularly for a reliever. Lots of guys are up there just trying to muscle up and embarrass some folks. That's not Reed. He has an idea of what he's trying to do and understands that moving the ball around keeps hitters off balance. His execution sometimes leaves something to be desired, which is problematic given that he's a flyball pitcher.
Reed is obviously a late-inning guy right now and actually has some development left in him. If his fastball command continues to improve or his slider adds some bite, he could become an elite closer to match up against any hitter in the league. If asked to guess, I would venture he never quite gets there. There's something fundamentally awkward/goofy about his game that prevents the kind of regular repeatability he'd need to make the kind of leap I'm talking about. His struggle with his slider in '12 is a case in point. A guy drafted out of college as an advanced reliever should be falling out of bed throwing a real slider. So his continued success speaks both to his skill with the fastball but also to the rub that mars the surface. His feel is good, not great. Same with his ceiling.