The MLB-best Tampa Bay Rays were dealt a big blow on Tuesday, as ace Tyler Glasnow was diagnosed with a partially torn ulnar collateral ligament and a flexor tendon strain, according to ESPN's Jeff Passan. 

The current plan is for Glasnow to try to rehab the injury in order to avoid Tommy John surgery. There is no timetable for his return.

The 27-year-old is 5-2 with a 2.66 ERA this season with 123 strikeouts over 88 innings pitched.