If you want the short answer without any of the gory details: Probably around the All-Star break.
More specifics after the jump.
A player earns a full year of service time once he amasses 172 days of action. Desmond Jennings accrued 33 days of service time last season. Super Two status –which essentially means the player gets four years of arbitration instead of three, i.e. more paying power earlier in their career— is supposedly going to be around 2.146 this season, although it varies year-by-year.
If you figure Jennings is a good bet to earn a full year of time in 2012 and 2013, then the Rays have 113 days (or so) to play around with. July, August, and September would give him around 90-to-95 days, meaning the Rays wouldn’t be too obvious about gaming his clock while also having enough time to potentially evaluate a Johnny Damon trade market (or get their fill of Sam Fuld, assuming Casey Kotchman isn’t somehow still on the roster and starting).
For those wondering why this is key, the Rays are really looking to do two things by keeping Jennings down. One is maximize the time Jennings will be their centerfielder (and rest assured, he’s a centerfielder regardless of the position he plays in the minors) while also maximizing their control length (ideally through Jennings’ prime years), and minimizing costs. The difference between a few months of Fuld and Jennings just isn’t worth the side effects of having Jennings up all year –at least not given the team’s reduced playoff chances.
Some may wonder whether this would also apply to Robinson Chirinos and the answer is no. Chirinos will turn 27 during the season, meaning he’s already under control through his prime years. Catchers don’t tend to age well, but since he’s a relative newbie, one has to wonder whether he can hold up a little longer than the generic backstop.
Of course, I don’t think the Rays would want to endure Super Two status with Chirinos either, so they may elect to wait until the middle of June or even longer while assessing Kelly Shoppach’s trade value.