https://www.mlb.com/news/inbox-rocker-o ... 2021-draft
When Jonathan Mayo ranked the top 20 prospects for the 2021 Draft shortly after the 2020 Draft ended, he listed Vanderbilt right-handers Rocker and Leiter in the top two spots, in that order. I look at Rocker as having the higher ceiling and Leiter as having the higher floor, and I'd take Rocker right now because he has more track record. Leiter has pitched just 15 2/3 innings at the college level, and I could see changing my mind after a (hopefully) full college season next year.
Rocker's advantages are a stronger build (6-foot-4, 255 pounds versus 6 feet, 195 pounds), a bigger fastball (capable of sitting in the mid-90s and climbing to 99 mph) and a more overpowering breaking ball (a wipeout slider at its best). Leiter has a deeper repertoire (90-95 mph fastball, quality curveball and slider, solid changeup that he barely used this spring), better delivery and more feel for pitching.
I ran this question by seven scouting officials: one director, one assistant director, two crosscheckers and three area guys. Five of them went with Rocker, though several of them admitted they hadn't had much of a chance to see Leiter in college.
My hot take is that Leiter might be able to Mike Leake it and skip the minors if he gets to pitch next year. Obviously much higher ceiling than Leake, Leiter has it all with a deep repertoire, health, great delivery, command, and control.