I agree with Bosox that velocity—or speed, whatever you want to call it—is overrated. There are plenty of pitchers around who, no matter what they do, will never be able to throw 100 miles an hour or what have you.
So—you could become a finesse pitcher, develop a good arsenal of breaking stuff, three or four such pitches, and work like mad on control, placement, keeping the batters off balance. And you’ll find that even an 81-mile-an-hour fast ball will look as if it were coming in there at 100 miles an hour.
I remember my pitching coach telling me once that he threw a so-called fast ball at 85, 86, and to the batter it looked as if it were coming in there at 106, because of how he set up his pitches. I myself managed to find an 81-mile-an-hour fast ball, and he told me that I could use that, along with my other stuff, to set batters up for old Filthy McNasty—the devastating slider that was my strikeout pitch. So don’t worry about the speed. Concentrate on control, on working to the corners, on getting the ball smack-dab into the pocket of the catcher’s mitt, and you’ll come out all right.