Castellanos has experience playing all over the field - OF and IF. So it wouldn't be a stretch that he gets called up if someone like, say James Loney, doestn' catch fire. Rivera can move to 1st and Castellanos can play in LF - providing he continues to hit in AAA.

If Castellanos makes the big club it will be as a 2nd Baseman. I think he will be the starting 2nd Baseman by 2014 at the latest. Either Van Slyke or Sands will get a call up before Castellanos. If Loney doesn't start hitting, and Sands doesn't start hitting right handed pitching, Van Slyke will get the first opportunity to replace Loney.

castellanos just tripled again, sands with RBI single http://mlb.mlb.com/mlb/gameday/y2010/index.jsp?gid=2012_04_17_iowaaa_albaaa_1

"Castellanos has MONSTER power for a second basemen while Ellis is as close to an Auto out as there is in the league. "

The question is whether that translates to the MLB level. If he could fit in at one of the corners that would be where something could be entertained. The production at the plate from those positions is non-existent. Ellis fits in fine at this point in time. The real deficiencies are elsewhere.