The Mets placed Sheffield on the 15-day DL and recalled left-hander Jonathon Niese from Triple-A Buffalo to start Saturday night against Houston.
Niese was set to pitch in place of Fernando Nieve, one of 10 Mets on the disabled list. Nieve tore a muscle in his right thigh Sunday while trying to beat out a grounder in Atlanta.
Two days before that, Sheffield got hurt while chasing Yunel Escobar's double. He was placed on the DL retroactive to July 18.
The 40-year-old Sheffield leads the team with 10 homers and is batting .286 with 36 RBIs in 75 games. He was signed just before the start of the season after getting cut by Detroit.
Sheffield was dressed in his uniform about two hours before Saturday's game and told reporters that the Mets had told him nothing. On the lineup card posted in the clubhouse, he was listed as an available bench player.
But the outfielder was called in for a 5-minute closed-door meeting with manager Jerry Manuel and assistant general manager John Ricco about 90 minutes before the game.
"Everybody came to an agreement that this is the best move to make, being on the more cautious side," Sheffield said.
Sheffield said he felt good enough to play. He hit several homers to left field during batting practice.
"I don't feel it," Sheffield said. "I don't feel it when I run, I don't feel it when I do anything. I'm not going to say this is a 'phantom' DL or whatever. Nobody knows when it comes to a hamstring. You can think you're ready, and go out there and it might be longer when you do it again.
"They always say when you have a bad hammy, when you're ready, give it another week," he said. "So that's the perspective I'm going to keep."
Manuel said the Mets leaned on the cautious side with Sheffield as they await the returns of other players with more serious injuries. Manuel is optimistic that shortstop Jose Reyes will return within two weeks after missing nearly two months with calf and hamstring problems.
"We feel that some people are near [coming back], and that if we took a chance and it didn't work out, instead of gaining people, we'd just be shuffling people back and forth," Manuel said. "We felt that was the best direction to go."
Reyes, the Mets' regular leadoff hitter, has been working out at the team's spring training facility in Port St. Lucie, Fla. Manuel said Reyes is running well again.
"Every day, he's doing well," Manuel said. "He has not had one setback. The progression that he's making sounds very favorable for him to be back [in] 10-14 days, somewhere in there."
Mets spokesman Jay Horwitz also said right-hander John Maine will see orthopedic surgeon Dr. James Andrews on Wednesday to get a second opinion on his injured pitching shoulder. Maine has been on the DL since June 7 and said after a simulated game this week that he was still feeling discomfort.