I guess I'll assume the pitcher has low 90s Velo, and 3 good pitches.
I've heard how anyone can play in college with hard work, but only some can play pro. Your thoughts on this?
What separates college and pro pitchers?
Velocity to an extent. Pro pitchers consistently throw harder on average than college kids.
Consistency with throwing strikes. Pro pitchers are close to 70% strikes. College kids are less.
Command of off-speed pitches. Pro pitchers can throw their off-speed in any count. Most college pitchers can't.
Physical conditioning. Pro season is 140+ games in the minors and 160+ games in the majors. It's only 50-70 or so games in college.
Mental toughness and capacity to think smart. Pressure is personal. But the higher stakes at the pro level can be tough for many prospects.
I would add to this the ability to have command of their pitches. I have seen college guys throw 80% strikes and get hit. Every fastball was in the same place....mid thigh middle of the plate. Being able to command pitches to the corners as well as up and down for strikes and get swings on balls that move off of the plate is huge.The jump from high school to college is giant, the just from college to pro is giant as well.