His key hit in the ninth inning tied the game after former Mets closer Francisco Rodriguez helped waste a six-run lead, and Casey McGehee followed Fielder with a two-run single that lifted the Brewers to an 11-9 win over New York on Saturday.
Milwaukee took an 8 1/2-game lead on St. Louis in the NL Central, matching the largest division lead in franchise history. Fielder is 9-for-18 with four homers and 12 RBIs against the Mets this season.
"When you're on a winning team, it makes you forget about yourself," Fielder said. "You're winning and your natural ability comes out and takes over."
Angel Pagan hit a two-run homer off Rodriguez (5-2) in the eighth that put New York ahead 9-7. Mets reliever Jason Isringhausen (3-3) couldn't get an out in the ninth and left after a bases-loaded walk.
"I usually figure it out," Isringhausen said. "But today, there was no figuring it out. I just couldn't find the strike zone."
The Mets scored five times in the seventh to close within 7-6, then took the lead against Rodriguez. Mets fans jeered K-Rod, traded with his hefty contract from New York to the Brewers during the All-Star break.
Rodriguez retired Ronny Paulino and Jason Pridie in order before coming undone. Ruben Tejada walked with two outs before Josh Thole's double went off the glove of center fielder Jerry Hairston, who had to change his course to the ball at the last second.
As the ball hit the ground and the crowd at Citi Field roared, Rodriguez put his hands on his head, staring out to center field.
"I thought it was a ball that was going to be caught," Rodriguez said.
Pagan made it worse for Rodriguez, sending his pitch into the upper deck in right, just one section over from where Fielder hit a three-run homer in the third that smacked off an empty seat with an audible report after barely staying fair.
"He hit that ball so hard, it didn't have a chance to hook," Brewers manager Ron Roenicke said. "We talk about solo home runs, they can win games late. But three-run home runs that are huge win games early."
Isringhausen walked the first two batters in the ninth, gave up a single that loaded the bases and walked pinch hitter Mark Kotsay on a full count, making it 9-8.
Acosta came on and retired Braun on a fly to right field, but Fielder came through against the Mets as he has all season. Fielder reached down and golfed an RBI single just past diving second baseman Justin Turner, and McGehee rolled his two-run single to right.
The Mets have lost eight of 10 since an inspired pair of comebacks against San Diego's strong bullpen. Saturday looked as if it was going to be another rollicking comeback -- for a moment.
"We lost the game, but in my estimation, it didn't go to waste," Mets manager Terry Collins said.
Chris Capuano struck out seven and made it 24 starts in a row in which he's gone more than five innings. That was about all the Mets left-hander could hang his hat on, though. He was pulled with the Mets trailing 7-1 in the sixth after giving up Betancourt's homer and two straight singles.
Collins had apparently seen enough, bringing in Pedro Beato to face Wolf with two outs. Wolf grounded out on two pitches and stayed in the game until leaving with one out in the seventh, still in line for the win before all the drama kicked off.
"To me it was more gratifying to come back and win," Wolf said. "It's one thing to have a (six)-run lead and blow it, another to come back."
John Axford pitched the ninth for his 37th save. ... Mets SS Jose Reyes did more running Saturday as he rehabilitated his strained left hamstring. Collins observed the workout and said Reyes looked "terrific" and that the Mets would see how he feels on Sunday before deciding on their next step. Reyes is eligible to come off the disabled list Tuesday, but probably will take longer than that. ... Rutgers football player Eric LeGrand was a guest of the Mets and was on the field before the game. He is still in a motorized wheelchair while he recovers from a serious spinal injury, though he has been standing frequently. LeGrand recently also visited the New York Jets' training camp ... Brewers right-hander Yovani Gallardo (13-8) was set to face Mets knuckleballer R.A. Dickey (5-11) in Sunday's three-game series finale. Gallardo has tied a career high with 17 quality starts out of his 27 this season. ... Capuano went 44-48 for the Brewers from 2004-2010. He won June 7 when he faced the Brewers in Milwaukee. ... A fire at one of the auto businesses across the street from the center-field entrance to Citi Field sent black smoke billowing into the air behind the scoreboard, momentarily distracting fans.