The Mets scored seven unearned runs in the eighth inning to break open a tie game. New Jersey Gov. Chris Christie was in attendance with his family while on vacation.
While facing Matt Clark with two outs, Medlen threw an off-speed pitch, grabbed his right elbow and turned his back to home plate. He then removed himself from the game.
Medlen, picked to start on opening day, was examined by Mets physician Dr. Struan Coleman and diagnosed with a right forearm strain pending an evaluation back at the Braves' complex on Monday.
Medlen was 15-12 last year with a 3.11 ERA in 197 innings for the NL East champions. The 28-year-old right-hander had Tommy John surgery in 2010.
"Obviously, any time a pitcher walks off the mound and meets you at the foul line, you worry about that stuff," Braves manager Fredi Gonzalez said. "But after everything kind of settled down, we're optimistic it's nothing really major."
Gonzalez said he talked to Medlen briefly during the pitching change and again inside the clubhouse afterward.
"He wasn't in good spirits. But after he got settled down a little bit and the trainers looked at him, I thought he was in better spirits," Gonzalez said.
Medlen did not speak with reporters but relayed a message that he will be available Tuesday in Orlando.
Braves catcher Evan Gattis said Medlen had good stuff through three innings.
"He was executing pitches, and the next thing you know -- I don't know what he grabbed -- but I knew it was his arm. It's never a good sign, never a good feeling, to be out there and see a pitcher walk off the mound like that," Gattis said. "On the last pitch, he just threw a yanked changeup -- I've never seen that -- and immediately there was a problem. ... He was throwing good pitches, and then it was just an out-of-the-blue kind of thing."
Mets: Though his numbers were solid in his second start this spring, New York right-hander Zack Wheeler wasn't happy with his effort.
Wheeler tossed three scoreless innings and gave up three hits, striking out three and walking one. Still, he said: "I'd like to forget what I did out there."
Wheeler, who grew up near Atlanta, said he experimented against the Braves and tried a few different things, such as throwing changeups to right-handed batters.
"Today was really just about going out there and working on some stuff, just because you face those guys tons during the season. I was trying to work on my changeup some today, and I was a little erratic," he said.
Braves: Gonzalez said Mike Minor, recovering from a urinary tract procedure on Dec. 31, continues to make progress and might be ready for the start of the season.
"It would be close," Gonzalez said. "We could bump him into the back (of the rotation)."
FIRST TIME OUT
Mets closer Bobby Parnell made his spring debut by coming on in a familiar spot, the ninth inning, but with his team up 8-1. The right-hander had not seen game action since last July 30 due to a herniated disk in his neck.
Parnell gave up a leadoff double to Mark Hamilton, who eventually scored an unearned run.
"It was just, throw strikes and work on your mechanics. I really wanted to know what my mechanics were going to be like in a pressure situation, in an adrenaline situation. I wanted to go out there and face hitters and find that," Parnell said.
Mets manager Terry Collins was glad to see Parnell go after some hitters.
"To see him out there for the first time and really see him let loose -- he's been a little tentative in the `pen and I understand it," Collins said. "He threw the ball great. The last five or six he let the ball go good."
The Mets will host the Marlins on Monday, but they won't face NL Rookie of the Year Jose Fernandez, who pitched against New York in Port St. Lucie last Wednesday. Miami manager Mike Redmond has opted to go with lefty Brad Hand, and Fernandez is scheduled to get his work in by tossing a simulated game.