When are the big time prospects gonna get called up?

There isn’t a hard date for that. Essentially a player can get to arbitration status (and thus a payout above the league minimum) a year early — in his 3rd year, instead of his 4th — if he accumulates enough service time. But “enough” is complicated: there’s a group of players who have more than two years and less than three years service time, AND have at least 86 days of service time in the preceding year. Call this group of players “Super Two Eligible.” A particular prospect in this group will actually get Super Two status if he happens to be one of the top 17% in terms of service time. So whether or not a rookie ends up getting Super Two status two years from now depends on how many other rookies got called up ahead of him (assuming he doesn’t get sent down again or put on the 60 day DL, both of which stop his service time clock).

In practical terms, it usually works out that if a guy doesn’t come up until sometime in June, there are probably already enough guys across MLB called up ahead of him that he won’t be among the top 17% in service time when he arrives at the point (more than 2 years, less than 3) where he might qualify for Super 2. So the team gets to pay him the minimum one more year instead of going through arbitration. And that’s why you start looking for the prospects to arrive after Memorial Day.

Needlessly complicated and confusing, right? Don’t worry, it’s likely to entirely change this offseason when the Collective Bargaining Agreement gets renegotiated. (And we’ll get some other even more arcane rule instead)