Los Angeles Dodgers slugger JD Martinez is dealing with a painful mystery injury, and had a difficult time explaining the ailment to the press as he struggles to walk.

“Nobody knows, including myself,” Martinez said when asked what it could be, per Mike DiGiovanna of the LA Times. “It’s weird because it tightens up on me, and then I can’t even walk, and all of a sudden, a day later, I feel perfectly fine.”

The 35-year-old is in his 14th MLB season, and first with the Dodgers after leaving the Red Sox after five years and signing to LA in the offseason. He has dealt with many injuries before over his career, but is baffled by the nature of this on and off pain.

“The same thing happened in Texas right before the game, boom. We’re trying to figure out what’s causing it, what’s triggering it. The MRIs look good, so I think it might be some kind of fatigue or something,” Martinez elaborated.

Dodgers manager Dave Roberts is certainly concerned about the strangeness of the injury, and hoping that it is a short term pain that they can figure out and eliminate.

“It’s hard to pinpoint, but I think the epicenter is the back, which is kind of manifesting itself in the hamstrings and the groin area,” manager Dave Roberts said. “He will probably do more of a full workout [Thursday], so best-case scenario is he could potentially be available [Thursday night].”

Martinez is hitting a middle of the road .260, but is brining the power and excitement with 25 homers and 75 RBI's to help the Dodgers get clutch scoring. He has been a critical piece to win close games, and they will need him down the stretch in a tough NL West battle with the Giants and Dbacks.