Not every great prospect turns into a solid addition to a major league roster, but it is nice to see him come through his injuries and at least get into a game. He is a step above 4A at this point. I do not think he is even close to the pitcher before the shoulder injury, but his game was not consistent of a bulldog pitcher.
He no longer has the stamina to last long. I think he is a bit more in the 88-90 range on the four seamer, but he should focus more on the two seamer as it has some late life on it. If I were making the call, I would have him scrap the slider and try to focus on off speed that does not command much pressure. I think he throw a circle change and maybe adding a something that could drop. He has long fingers for his small statue, why not try a palm ball or a non snapping forkball.
His baseball life can only be extended with stuff that works the bottom of the zone. Usually, guys with shoulder or elbow injuries are best to eliminate curves, slurves, sliders, and any type of "snapping" pitches.
I think you can see him make the bullpen out of ST because he is left handed and can get out left handed batters. You can make a long career out of it with that low riding two seamer.