Putz was put on the 15-day disabled list Friday. The surgery on his pitching elbow is scheduled for Tuesday.
Picked up in the offseason to lock down the eighth inning ahead of new closer Francisco Rodriguez, Putz is just 1-4 with a 5.22 ERA and two saves for the Mets. He has allowed eight runs and nine hits in 1 1-3 innings in his most recent outings. He complained of pain after Thursday's game in Pittsburgh.
"That's why he's pitching not the way we're used to seeing J.J.," New York general manager Omar Minaya said before the Mets' game with Washington.
Minaya said Putz wouldn't begin throwing for at least six weeks, and estimated his return in "anywhere between 10 and 12 weeks."
Putz has been bothered by elbow inflammation this season, and received a cortisone shot on May 14, but that hasn't helped.
"The condition got worse in the past couple of weeks," Minaya said.
New York purchased the contract of right-hander Fernando Nieve from Triple-A Buffalo. He was 3-0 with a 3.70 ERA in four starts with Buffalo.
Mets manager Jerry Manuel said Nieve would be used in the bullpen.
Bobby Parnell will be Rodriguez's setup man in Putz's absence, and Manuel will search for a seventh-inning option.
"It's going to be very challenging for us," Manuel said. "Everybody's going to get a shot."
Shortstop Jose Reyes, who's been on the 15-day DL for right calf tendinitis since May 21, will rest for two days after sustaining a tear in his right hamstring during an extended spring game on Wednesday in Port St. Lucie, Fla.
Minaya said that he wouldn't estimate a time for Reyes' return. "All the tests that he's been given are positive and encouraging," he said.
In Reyes' absence, Minaya said he's comfortable with Alex Cora and Wilson Valdez at shortstop. Cora has been hampered with a ligament tear in his right thumb, and he said he'll try and postpone surgery until after the season.