Over on the AVG as this guy can hit and has done so at every level so far, but under on the HR and RBI. I can see him hitting quite a few doubles, but combining the fact that he's not known as a power hitter and that he's in a bit of a park unfavorable to power, I wouldn't be looking at too many HR's from him. I'll probably lean towards over on the SB's. He runs decently for a 3B and 5 probably isn't too much to ask for, but that's too dependent upon how often they would send him to make a confident guess.
As far as job security concerns, I've heard they traded Castilla so the job would be Zimmerman's. Considering that and the weak FA market for 3B and also that they would be hard-pressed to find a 3B as good defensively as Zimmerman is capable of being, I expect the job to be his to lose entering ST.