It's a huge blow to the Mets, even though Wagner has blown seven of 34 save chances. No other New York pitcher had a save this season until lefty Scott Schoeneweis secured Tuesday night's 6-5 victory over San Diego.
"It's just a bad time to have to go through something like this," Wagner said.
Struggling setup man Aaron Heilman got the first shot at closing in Wagner's absence, but it didn't last long. After entering in the ninth with a four-run lead, Heilman walked his first batter on four pitches and gave up a three-run homer to Jody Gerut with one out.
Mets manager Jerry Manuel yanked Heilman and then played the percentage matchups with Joe Smith and Schoeneweis, who retired left-handed hitting Brian Giles on one pitch for his ninth major-league save.
Afterward, Manuel said he wasn't sure who his closer would be going forward.
"We've got enough men to get it done," the manager said. "We'll be fine. They'll step up, and Aaron will come back and he'll do well. I feel very confident we'll get him back."
Before the game, the Mets also recalled right-hander Ruddy Lugo from Triple-A New Orleans. He has been starting games in the minors and will be penciled in as a long man out of the bullpen with New York.
After losing their final four games on a 1-5 road trip, the Mets opened a seven-game homestand Tuesday night. New York is third in the NL East, two games behind in the division race and three in the wild-card standings.
Wagner had an MRI exam and X-rays on his pitching arm Tuesday. The tests showed no structural damage, but the forearm strain requires rest.
"It's like a pulled hamstring," he said.
The left-hander is 0-1 with a 2.30 ERA and 27 saves in 45 appearances. After sitting out a game with a sore shoulder two weeks ago, Wagner began feeling discomfort near his elbow while pitching in Florida last Tuesday.
He saved that game but then squandered a two-run lead in Saturday night's loss at Houston. Wagner said the pain and tightness in his arm made it difficult to finish his pitches, especially when aiming inside, and the team couldn't count on him because he was unable to pitch two days in a row.
"When they can't rely on you, you're worthless," he said.
Manuel first indicated he might go to a closer-by-committee approach but then said the experienced Heilman was probably his best "crossover guy" in save situations because of his ability to get righties and lefties out.
"I've always said, in order for us to be really what we need to be, we need other guys to be able to close games. I didn't know we would be forced into that," Manuel said. "It's going to be important that some guys step up."
Heilman, who is 1-6 with a 5.67 ERA in 59 games, took consecutive losses Friday and Saturday in Houston. He has six major league saves -- five in 2005 and one last year.
"I've closed a few games before, so that definitely helps. Did it a little bit in college," Heilman said. "I don't feel like I'm going out there naked."
When starting pitcher John Maine (shoulder) went on the disabled list Sunday, the Mets called up 22-year-old reliever Eddie Kunz from Double-A Binghamton, where he had 27 saves and a streak of 17 scoreless innings over his last 16 appearances.
But Manuel said he'd prefer to bring Kunz along slowly and get his feet wet with some success in New York before handing the pressure-packed closer's role to him in the big leagues.
A rehab program will be determined for Wagner, who said he hadn't picked up a ball since Saturday. The Mets hope he can return to the mound as soon as he's eligible to come off the DL on Aug. 18 at Pittsburgh.
Lugo, the younger brother of Boston shortstop Julio Lugo, was a high school star in Brooklyn. He was expected to arrive at Shea Stadium in time to be available out of the bullpen Tuesday night.
With Maine sidelined, Oliver Perez is scheduled to start Friday night against Florida on four days' rest. The Mets need to find a starter for Saturday.
In other injury news, right fielder Ryan Church (post-concussion syndrome) took batting practice and worked out before the game. The Mets are waiting for doctors to clear Church for a minor-league rehab assignment.
Second baseman Luis Castillo, on the disabled list with a strained left hip flexor, was scheduled to play a rehab game Tuesday night for Class A St. Lucie.
Relief pitcher Ambiorix Burgos, recovering from elbow ligament replacement surgery, pitched two innings in his first rehab game for the Gulf Coast League Mets. He struck out four and walked none, allowing two runs and three hits.