MIAMI — As Jacob deGrom ramps up for a potential return to pitching this season, the Mets on Tuesday provided a clearer explanation for the right-hander’s two-month absence from the mound.

Team president Sandy Alderson acknowledged deGrom was dealing with a “sprain” in his right elbow. Alderson called it the “lowest-grade” of a partial tear in the ulnar collateral ligament.

DeGrom underwent Tommy John surgery after he was drafted by the Mets in 2010, but Alderson said such action isn’t needed in this rehab.

The sprain diagnosis contradicts previous messages from the organization that deGrom wasn’t dealing with a structural issue with the elbow.

“This is a very low-grade thing that has resolved itself,” Alderson said before the Mets faced the Marlins. “The ligament is perfectly intact at this point. Whatever condition existed before has resolved itself and that is one of the reasons he didn’t pitch for a period of time.”

DeGrom played catch before Tuesday’s game — in the last two weeks he has gradually increased the distance of his tosses to beyond 100 feet. The goal is to ramp up deGrom enough to test him on a mound, perhaps in a game before the season concludes.

“By ramping him back up what we’re trying to do is recreate that pain to see what his threshold is and hopefully it doesn’t get replicated,” Alderson said. “That doesn’t mean we’re going to ramp him up until it breaks. My point is we have to begin to see if this is more of a chronic issue that relates to mechanics in some way, but the more we know going into next season the better off we will be.

“I don’t expect he is going to get ramped up higher than 75 percent before we have an idea where this is going. In terms of him pitching the rest of the season, I think that is still very much up in the air.”

The Mets ace was enjoying a historic season (pitching to a 1.08 ERA in 15 starts), albeit one marred by various physical ailments that shortened his outings before he was placed on the injured list after returning from the All-Star break with discomfort in his forearm.

DeGrom has averaged 99.2 mph with his fastball velocity this season, the highest in MLB. Alderson was asked about the potential correlation between that velocity and the pitcher’s elbow issues.

“I don’t know exactly what caused the problem, but if you were to look at it generally throughout baseball, I think velocity has something to do with a lot of these injuries,” Alderson said. “Whether it’s true in his case or not I don’t know. But I think there is some correlation. I am not a doctor, I haven’t done the research, but I suspect there is a correlation between the velocities pitchers exhibit today and the rate of injury, which is a concern across baseball.”

Alderson said he’s unsure if it’s realistic to simply tell deGrom not to throw as hard.

“It’s hard to know how one imposes those limitations and then enforces them,” Alderson said. “So I don’t know.”