It didn't even faze him this time.
"I feel very good about big Mike," manager Jerry Manuel said. "He has really evolved and matured into a solid, solid pitcher."
Pelfrey (6-1) allowed one run and six hits, lowering his ERA to 2.86. The right-hander buckled down after Cervelli's hit got the Yankees on the board, getting Randy Winn to bounce out to second with runners on the corners to end the threat in his final inning.
"I think the game as I would describe it has slowed down on me," Pelfrey said. "At times, I would have still been thinking about that play and I'm trying to get Winn out. But I didn't worry about that."
David Wright had a pair of RBI singles for the Mets, who scored all their runs with two outs. Angel Pagan finished with three hits and pinch-hitter Alex Cora contributed a key RBI single in the sixth at Citi Field.
"Two-out RBIs are a killer," Bay said, "and then just to kind of tack on one here, one there, it ended up we needed those runs at the end."
The slumping Yankees left 13 runners on base in their fourth loss in five games, making it difficult to overcome another subpar performance by Phil Hughes (5-1).
Kevin Russo's bases-loaded walk against Fernando Nieve trimmed the Mets' lead to 5-2 in the eighth and brought Manuel out of the dugout. Francisco Rodriguez came in and allowed Derek Jeter's run-scoring grounder before retiring Brett Gardner on a bouncer to third to end the inning.
K-Rod then pitched the ninth for his seventh save in nine opportunities, striking out Cervelli with runners at the corners to end the game.
"He did his job," Manuel said.
Teixeira went 0 for 4 with three strikeouts. It appeared he was on his way to ending his customary early-season slump when he got off to a fast start this month, but now is stuck in a 1-for-20 rut over his last five games.
"I feel terrible," he said. "I won't get any worse than right now."
Hughes allowed four runs and eight hits over 5 2/3 innings in his first loss as a starter since May 9, 2009, at Baltimore. The right-hander was coming off his worst start of the season, a no-decision against Boston last Monday when he gave up five runs in five innings.
"I threw a lot of fastballs out over the plate," he said. "I didn't have command of the corners. The last couple outings haven't been good, especially command."
Bay scored three times in his 10th career four-hit game and first since June 23 for Boston at Washington.
The first Subway Series of the season concludes with a marquee pitching matchup Sunday night. Two-time AL Cy Young Award winner Johan Santana is scheduled to face Yankees ace CC Sabathia in the rubber game of the set.
Sabathia is 3-1 with a 2.57 ERA in four career starts against Santana, according to STATS LLC. Santana also was roughed up in his last start against the Yankees, allowing nine runs over three-plus innings in a 15-0 loss last June.
"It's going to be fun and, at the same time, it's going to be challenging," Santana said.
The Mets needed just one inning to better their total from Friday night's 2-1 loss. Wright and Pagan had consecutive RBI singles in the first to stake Pelfrey to a 2-0 lead.
Wright added another run-scoring single in the third, and Pagan doubled in Bay in the seventh.
Wright began the day mired in 4-for-33 slump over his last nine games, and was among the major league leaders with 57 strikeouts. New York also was batting .221 with runners in scoring position and two outs entering the game.
Yankees manager Joe Girardi said it's too early to tell if RHP Javier Vazquez will be able to make his next start. Vazquez bruised his right index finger while bunting Friday night. "Gripping the ball was OK," Vazquez said. "I should be able to throw the bullpen Monday or Tuesday." ... Mets CF Carlos Beltran (right knee surgery) is running and swinging a bat in his rehab program in Florida, but Manuel said he hasn't progressed to "full-out baseball activities" yet.