Opposing catcher...(Victor Martinez is easy to steal on, for example)...I think this may be the best way to guess for people who aren't given their bucks to steal, like Pierre or Crawford.
Tempo of the offense...(if you're hitting the cover off the ball, you don't need to jump start the offense with stolen bases)
The player's actual level of play at the time, matters as well. If he's not getting on as consistently, he won't get that many chances to steal.
Basically, stolen bases are a gimme...it's hard as hell to predict them, even during the preseason. You never know when a manager will give the green light and when he'll rescind that.