Kansas City Royals pitching prospect Kyle Zimmer was supposed to be activated this week. Instead, he will spend additional time on the minor league disabled list. A throwing session on May 19th did not go well, and Zimmer has been diagnosed with a strained latissimus dorsi muscle. There is no firm timetable for Zimmer's return, but he will be out at least a couple of months. He's not even supposed to start playing catch again until early July.
Zimmer was expected to make his major league debut sometime this summer. That's theoretically still possible, if he comes back strong in July, although at this point expectations should be kept very small for any kind of 2014 big league impact.
A healthy Zimmer is Kansas City's best minor league pitching prospect, with a 95-100 MPH fastball, above-average slider and curveball, and a workable changeup. At his best he has both the stuff and command to be a number one starter, but durability looks like a concern. He was shut down early last year with a sore shoulder and his inability to get back in gear this spring is disappointing.