Kelly was committed to LSU and was the second LSU commit to be selected in the draft, behind only Brian Turang who went 21st overall.
What MLB has to say:
Kelly was emerging as a top high school prospect in West Virginia when he made the move to IMG Academy in Florida after his sophomore year. He’s taken advantage of the opportunity, showing off premium arm strength against a very high level of competition. Kelly is all about arm strength and a big fastball. He’ll sit 92-93 mph consistently and has been up to 95 mph at times. His slider, which has 10-to-4 action with solid bite and depth, gives him a breaking ball that will be at least average. It can get slurvy at times but he has made strides with it this spring. He doesn’t use a changeup in games, though some have seen feel for a fringy one in bullpen sessions. The big right-hander has struggled with his command at times, with some feeling his high-tempo delivery and mindset point to a future in the bullpen. If a team thinks he’s a starter, he could go in the top five rounds of the Draft because of his arm strength. Signing him away from his commitment to LSU might be another variable teams will consider in June.
What Baseball America has to say:
Kelly transferred to IMG Academy this spring to play with Blaze Alexander and several other talented 2018 prep prospects. This spring, Kelly’s velocity has returned to the range that scouts have seen in the past, as the 6-foot-4 Louisiana State commit was in the upper 80s and low 90s over the summer but has regularly touched 95-96 mph this spring. He consistently pitches in the 91-92 mph range, though his fastball is fairly flat without natural movement. He has a fringe-average slider to go along with his fastball, though scouts note that both of those offerings would play up in the bullpen. With some effort in his delivery and a slight head whack, a reliever profile is what many scouts write down for Kelly, but his natural arm strength is exciting wherever he lands.
As a prep selection in the bonus pool rounds, the team clearly likes the potential they see in the young man and can be expected to develop him as a starter for at least a few years. Commitments to LSU are not easily broken, as the school is one of the elite feeders to the MLB ranks. However, the Diamondbacks had a plan for Kelly and managed to entice him away from college with a $350,000 signing bonus against a slot allotment of $158,500. Most can expect that Kelly will be assigned to short-season ball starting next season, spending the remainder of this year in training and then joining short season ball in 2019. Developing as a starter, the soonest anyone should expect to see the hard-throwing right-hander would be mid-to-late 2022. Even if he does wind up relieving, the timeline would not change much.