This.
Now that it's June, and minor league call ups no longer affect arbitration, and you get a free year out of them, something must be wrong with Montero for him not to be up in Cervelli's place. I can think of 3 scenarios.
1. Montero isn't the bat that the Yankees have proclaimed, and they're trying to hide that a bit to retain value at the trading deadline.
2. Montero's defensive skills are so absolutely horrid that even the increase in offensive production over Cervelli would be a waste because of the defensive drop off. And that's horrible, considering Cervelli just threw 3 balls in the CF.
3. They want Montero to be starting everyday, which he wouldn't do in the MLB because of players like Jeter, Posada, and A-Rod needing regular days off because of age, resulting in the need for a guy like Nunez to play their positions while they DH.
I'm not sure which of the 3 scenarios is in play, but regardless, none of them are good.