Acquired: Amateur Free Agent, 2012.
2014: Springfield Cardinals (A), Memphis Redbirds (A+)
(You can find the 20/80 grading primer here)
I look at those grades and immediately I think "reliever".
The fastball is sneaky good and gets on hitters quick. Petrick throws it from a high 3/4 arm slot and he gets a good downward plane on the pitch, hammering the bottom of the strike zone when he's on and getting a lot of ground balls, mostly up the middle of the field on either side of the bump.
The secondary pitches leave a lot to be desired. His curveball doesn't have a sharp break to it and he tends to cast it towards third base which gives it more a slurve movement rather than a hard, tumbling break. Think 10-4 rather than 11-5. Considering Petrick's arm slot you would expect his changeup to be a bit better, especially given the movement on his fastball, but it's a fringe average pitch that he doesn't seem comfortable throwing even when he's ahead in the count.
Petrick's pitchability grade is high due to his deceptive delivery, which not only hides the ball well, but also adds life to his mid-90's fastball. I really don't have any good video of Petrick that's worth posting on the blog (and I couldn't get the rights to the spring training broadcast on FSMW from last spring) so about the best I can do is link you to the unofficial video and then talk about it.
Petrick tends to wrap his wrist a bit behind him as his arm drops and his motion to the top is a bit of a short arm slinging action. That keeps the ball behind him for most of his delivery, and the hitter only sees it just prior to release. It's hard for hitters to get their timing down since Petrick throws 94-95 on a regular basis.
The problem, of course, is that once a good hitter has a PA or two against Petrick the fastball loses some of it's luster as they figure out where to pick the ball up. Consequently, Petrick's effectiveness drops off much more than someone like Tim Cooney in his second and third trips through the lineup because he doesn't have a good offspeed pitch to fall back on and keep hitters off balance. They'll just set dead red on the fastball and put a good swing on it.
Those issues tend to go away in the bullpen since no hitter would see him more than once on a given night or more than a couple times in any series of games. It's also possible that he could add a tick or two on his fastball when throwing in shorter stretches. A 95-96 mph fastball that can touch 97 and has a lot of movement? Sounds a lot like a right handed Kevin Siegrist, doesn't it? I think even his minimally effective secondary pitches would work better in limited innings and he could face fewer left handed hitters, who seem to give him more trouble.
Remember: This is a guy that nobody thought was good enough to put him in the top 1500 players in the draft in 2012 or 2013. An undrafted free agent getting to AAA is a huge win for the club -- turning that guy into a quality middle innings reliever for 2-3 years would be a coup.
Petrick did pitch some out of the bullpen late last year as Memphis made their run to the AAA playoffs and put together a quality start during the playoff series. I would guess that he'll likely start the year in the rotation and maybe move to the bullpen if he can't improve on last year. Given the current depth among right handed relievers at the big league level (and flamethrowers like Sam Tuivailala and Chris Perry barking up the door behind him), Petrick is still more depth than anything else, but depth among middle relievers is a good thing to have given how fickle they are from year to year.