The Mets thought Maine was close to coming off the disabled list. He had been scheduled to make his second minor league rehab start Saturday, this time for Class-A Brooklyn, but he felt pain in the back of his shoulder while playing catch Thursday.
"It's similar to what it was before," Maine said Friday.
The right-hander had a second cortisone shot and won't throw for about a week. He'll be re-evaluated after that and said he hopes to return after the All-Star break.
"It is frustrating," Maine said. "Even if I can go out there and just have a little bit of soreness, I would pitch. But I can't go out there with pain. It's not going to do me any good, it's not going to do the team any good. And I tried. I tried to come back and throw. But I just couldn't, so I just had to say something."
Maine and general manager Omar Minaya said tests showed there is nothing structurally wrong with the pitcher's shoulder. Maine has been out since June 7 with what the team called weakness in his right shoulder.
"It's just a pinched nerve," Maine said. "They said that there's inflammation back there which is causing everything. Just let it go down and then start exercises and start throwing and it should be good."
After last season, Maine had arthroscopic surgery Sept. 30 to remove a lesion from the back of his shoulder socket. He is 5-4 with a 4.52 ERA in 11 starts this year.
Perez, on the DL since May 3 with tendinitis in his right knee, is still slated to make a rehab start Sunday for Brooklyn. He probably needs two or three minor league outings to increase his pitch count to about 100, which would put him in position to return, Minaya said.
But when he's activated, Perez might go into the bullpen rather than the starting rotation. Minaya said manager Jerry Manuel will make that decision.
Re-signed to a $36 million, three-year contract in the offseason, the erratic Perez went 1-2 with a 9.97 ERA in five starts this year before landing on the DL.
Also Friday, outfielder Gary Sheffield (right knee) was back in the lineup for the Subway Series opener against the Yankees.
The 40-year-old Sheffield missed a four-game series against St. Louis this week. He took a shot Wednesday behind his knee to relieve inflammation and a fluid buildup in the bursa sac.
The nine-time All-Star tested his knee during batting practice Friday, taking fly balls and running the bases. He started in right field, batting cleanup.
"Everything felt good," Sheffield said. "A lot better. I don't have to worry about, can I get to a ball or not? If I couldn't get to it, I just couldn't get to it. Not because I was limited."
Sheffield homered leading off the fifth inning for the Mets' first runner against CC Sabathia. It was Sheffield's 508th career home run and ninth this season, giving him sole possession of the team lead. He began the night batting .276 with 26 RBIs.
"The two extra days of rest kind of got me where I need to be," Sheffield said.
It was Church's 96th start and 115th major league game in center. Normally the Mets' regular right fielder, he was positioned between Sheffield and Fernando Tatis in the spacious outfield at Citi Field.
"See ball, go get ball," Church said, explaining his approach. "I do have my track shoes."