MILWAUKEE -- Mets starter Jason Vargas exited Sunday's 3-2 loss to the Brewers after four innings with left hamstring tightness and is being evaluated for the extent of the injury.

Vargas said he felt something in his hamstring on the last pitch after striking out Travis Shaw to end the fourth inning. He allowed three runs, all in the third inning, and he left trailing 3-0.

"I came in the locker room right away and kind of tried to get things assessed as quickly as possible in case we had to go to the bullpen," Vargas said. "As soon as we tried to recreate pitching and going through the motion of going toward home, it set it off again. It wasn't anything crippling, but I think it was definitely the right thing to do.

"I don't think I've ever had to deal with any hamstring issues, so I think it's more of a let's see how it is tomorrow, not panic, not rush to any conclusions, and we can make an assessment how some of the treatment has gone after the game, how some of the treatment tonight when we get to San Diego, and then how the treatment goes in the morning before we get to the field, as well. I think that gives us a pretty good baseline, and hopefully we can get a good idea of what we need to do after that."

Vargas, who entered 1-1 with a 5.75 ERA, allowed three runs on three hits with five strikeouts and no walks in the 50-pitch outing.

With the bullpen taxed in the Mets’ 18-inning, 4-3 loss Saturday night, manager Mickey Callaway said before the game that he hoped Vargas would approach his pitch limit. But the injury quickly changed those plans for Vargas and the Mets. Tim Peterson came on in relief after Vargas left the game and threw 2 1/3 scoreless frames.

"[Vargas] was throwing the ball great. He had a lot of pitches left, 60 pitches left or something," Callaway said. "Just unfortunate, he was throwing the ball well and just couldn't get through it."

Callaway said it was too early to tell if Vargas would miss a start, especially with an off-day on Thursday.

"I don't know at this point. We'll have to see how he comes in tomorrow," Callaway said. "We have a lot of flexibility. We haven't looked at it that closely since we just got off the field, but we'll make the adjustment if need be."