The Sky Is The Limit
Crystal Ball: Carl Crawford
This is a tough one. Crawford has gradually improved each year, boosting his power production while maintaining his speed. His plate discipline is still weak, inhibiting his on-base abilities, but his strikeout rate has come down, and he has enough bat speed to adjust even when he swings at bad pitches too often. Still, currently his OBP is heavily-dependent on his batting average.
Given a normal growth curve, Crawford should continue to add power. Given his outstanding athleticism, he should be able to maintain his speed production as he gets older. The main question now is how much his OBP improves, and I really don't know any way to predict that. I ran down my thoughts concerning Crawford in this piece last month: Thoughts on Carl Crawford. Note his list of comparable players: Claudell Washington, Jose Cardenal, Devon White, Willie Davis, Lloyd Moseby, Garry Madox, Mickey Rivers. Another good comparable is Vada Pinson.
For the Crystal Ball, we will assume that Crawford tops out in the lower 20s in home run production, that he increases his OBP abilities slightly but not massively, and that he maintains his speed for a long time. Given his athleticism and apparent durability, he is likely to have a very long career.
As always, the Crystal Ball isn't meant to be taken too seriously. There is nothing here to get bent out of shape about. Given what we know about Crawford so far, this Crystal Ball is one possible outcome, given the assumptions listed above.
You will note that this is a Hall-of-Fame quality career. Is Crawford capable of that? If he improves along a normal growth curve, and if he stays healthy and lasts long enough, yes.
But the same thing could have been said about guys like Pinson and Davis. Take it for what it is worth.