Francisco Cervelli is the sort of player that seems to rise above criticism - as a back-up catcher that hustles, there really isn't much to nitpick ... frankly put, most anything out of that position is gravy. However, Cervelli really hasn't given the Yankees much of anything. Since May 15, Cervelli is batting .197/.273/.243. Granted, that's a small sample size (177 PA) - but it's a much better sample to work with than his first 62 PA, in which he did incredibly well. Further, despite his defensive reputation, Cervelli doesn't appear to be much behind the plate - with -5 TZ, 2 passed balls, 22 wild pitches, and only 16% caught stealing, he isn't really an upgrade over Posada (-5, 4, 19, and 19%, respectively). In short, he's been terrible.
Again, it's difficult to ask for much out of the team's back-up catcher - but with Posada needing to sit two or three games per week, the Yankees situation is different from most other teams. Considering that (and Cervelli's ineptitude), I believe it's time to give Jesus Montero a shot.
Despite a horrific start to his Triple-A season, Montero is now batting a solid .271/.347/.460 on the season at 20. He batted .283/.324/.505 in June and .342/.441/.632 in July. His strikeouts are down, his walks are up, and his power has returned. While scouts and analysts remain split on his glovework, I doubt that he could be much worse than the current Yankees duo - and his bat is likely to surpass Cervelli's instantly.
The largest issue is whether or not this would stunt Montero's development, which is certainly a risky proposition. I, for one, am against rushing prospects, preferring to see a full year at Double-A and Triple-A (barring a Heywardian ascent). Montero has had his growing pains, but I think that he'd benefit a great deal from a call-up. He wouldn't be rotting on the bench (a la Buster Posey last season), as Posada needs frequent breathers. On those days that Montero did sit, he could work with Joe Girardi and Tony Pena, two very good defensive catchers, on his glovework. Working with pitchers that attempt to hold runners alone could help, for what it's worth.
In the end, the actual value that this would provide the team may very well be negligible. However, it certainly wouldn't hurt, and it would give the Yankees a far better idea of Montero's value for now and the future.