"Playing catch is a bit of a chore right now," Maine said after Thursday's game, which the Mets lost in extras, 6-3. "There's a little pain."
Earlier this week, Maine underwent an MRI that did not reveal any structural damage in the shoulder. The right-hander had surgery last September on his right shoulder blade after pitching in pain after the All-Star Break.
He blames the fatigue on the rigorous offseason workout regimen he employed to get back in shape following the surgery.
"I started Dec. 1, and I didn't take too many days off," he said. "Now it's kind of going to sleep on me."
Maine hopes that his stay on the DL isn't very long, though he admitted that it's unknown how long arm fatigue can last. He was hoping to avoid the DL and miss only one turn in the rotation, but back-to-back extra-inning losses to the Phillies may have prevented the Mets from playing short-handed in the bullpen for this weekend's series against the Yankees in the Bronx.
The Mets have yet to decide on a plan for Maine's rehabilitation, although it's likely he will be sent to Port St. Lucie, Fla. General manager Omar Minaya did not provide a timeline for Maine's return.
"I can't give a timetable on him, because it's going to be a rehab situation," Minaya said. "With John, he wants to go tomorrow, but this is the cautious thing to do with him right now."
The Mets decided on Friday that reliever Fernando Nieve will start on Saturday at Yankee Stadium in Maine's place. Nieve has thrown two scoreless innings for the Mets since being called up from Triple-A Buffalo on June 6.
Nieve was 3-0 with a 3.70 ERA in four starts for Buffalo this season.
To immediate take Maine's place on the 25-man roster, the Mets purchased the contract of left-hander Jon Switzer from Triple-A Buffalo. Switzer, who was signed as a Minor League free agent in January, was 0-2 with a 2.13 ERA in 25 1/3 innings with Buffalo. He had a 1.50 ERA since May 1.
The good news emerging from Thursday night's game as far as pitching is concerned was the performance of Tim Redding, who put up his second consecutive strong outing. Redding, who also experienced arm fatigue -- among other problems -- during the spring, will now be counted on to step into a larger role in the rotation in Maine's absence.
Tim Britton is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.