Hernandez, 34, was 7-8 with a 5.47 ERA, but had been especially poor over his last three starts, allowing 18 earned runs in 14⅓ innings. He allowed six runs in a 10-1 loss to the San Francisco Giants on Monday, and the Mets went 2-10 in his last 12 starts.

Wagner, who has not pitched since Aug. 2, 2008, was expected to miss the entire season after Tommy John surgery on his left elbow. The 38-year-old recovered much more quickly than expected, and the Mets plan to showcase him over the next week in hopes of generating trade interest.

The departure of Hernandez, who helped the Florida Marlins win the 1997 World Series, leaves another hole in a porous starting rotation. New York already is missing Jonathon Niese with a torn hamstring tendon and John Maine (FSY) with a shoulder injury.

Manuel said Tim Redding (FSY) will make a spot start Saturday against the Philadelphia Phillies. With the Mets well out of playoff contention in a season brought to pieces by injuries, manager Jerry Manuel said it's also possible the club will look at some young arms after rosters expand Sept. 1.

"From a manger's point of view, I probably always want to see youth at this point, but it has to be the right timing," Manuel said. "The player development people have to say a young player will come into this situation and not be hurt by it."

Manuel said he wasn't sure who might be ready for a look.

"This is a different place to come. New York is different, just in the sense of so much exposure," he said. "It's a little different here and we have to be careful of that."

Wagner has 385 career saves, but is likely to work the seventh or eighth inning in front of star closer Francisco Rodriguez (FSY). The Mets reportedly have placed Wagner on waivers, but he's unlikely to be claimed because of his $2.6 million salary and $1 million buyout for 2010. If he's not claimed, the Mets could be free to move him by Friday.

In other news, outfielder Gary Sheffield (FSY) was listed on the lineup posted about four hours before the first pitch Thursday night. His name was replaced by youngster Cory Sullivan (FSY) about 30 minutes later.

"He asked for a day off to kind of clear some thoughts and things," Manuel said. "I think it would do him good both physically and mentally to get a day."

Sheffield has said he isn't sure whether he'll be with the Mets the rest of the season, raising suspicion a deal could be in the works. With Carlos Beltran (FSY), Jose Reyes (FSY), Carlos Delgado (FSY) and David Wright (FSY) all out with injuries, Sheffield is left as the Mets' most productive hitter, batting .286 with 10 homers and 43 RBI in 88 games this season.

"Just for the best today," Sheffield said when asked why he wasn't starting. "It's just the best thing to allow somebody else to play. I'm 100% healthy."

Upon returning to the clubhouse after batting practice, Sheffield joked, "I'm still here."

Versatile infielder Alex Cora (FSY) had surgery on his right thumb and showed up at Citi Field wearing a cast. Cora plans to have surgery on his left thumb in about four weeks, but had the right hand operated on first so he could begin throwing.

Left-hander Oliver Perez (FSY), who's been dealing with a sore right knee, had a short throwing session before the game and pronounced himself fit to start Sunday against former teammate Pedro Martinez (FSY) and the Phillies.

"I'm feeling pretty good," Perez said. "I can pitch Sunday and I'm ready to go."