Hart robbed Tadahito Iguchi of what could have been a game-tying homer in the ninth, helping Cordero pick up his 34th save in 39 chances. Milwaukee remained a game ahead of the Chicago Cubs, while Philadelphia stayed five games behind the first-place Mets.
"I owe him," Cordero said. "I thought it was gone. But we have got Corey there. He is pretty tall, and he made a pretty good play. If it would have been 'Shousie' over there, it would have been a tie game."
Brewers reliever Brian Shouse -- who pitched a perfect sixth -- is generously listed as 5-foot-11 in the Brewers media guide. Hart is 6-6.
Milwaukee trailed 5-1 going into the bottom of the sixth inning and 5-4 heading into the eighth.
But with one out, J.J. Hardy singled. Ryan Braun popped out, bringing up Fielder, who hit a 1-2 pitch by Tom Gordon (1-2) deep into the right-field seats, sending the sellout crowd of 42,126 into a frenzy.
Hart caused another frenzy when he faded back on Iguchi's drive in the bottom of the ninth, scaling the wall in front of a picnic area to bring the would-be homer back.
"It kept carrying pretty good, so I just sprinted back there as fast as I could to see if I could make a play on the ball," Hart said. "If I am 5-8, I don't think that I get that ball. I am good for something, I guess: height."
Derrick Turnbow (3-4) pitched the eighth to get the win.
Phillies manager Charlie Manuel did not speak to reporters after the game, closing his office door. Starter Cole Hamels also didn't speak to reporters after the game.
Hamels, who remained 12-5, gave up seven hits and four runs in seven innings. He was dominant at the start as the Phillies built a 5-1 lead. But Milwaukee scored three times in the sixth on a two-run double by Hardy.
"Cole pitched great. He deserved to win, and our team deserved to win," Gordon said. "Tough game."
And a tough eighth inning.
"I was trying to go up and in and left it down," Gordon said of the pitch to Fielder. "I missed, and he made me pay."
Said Fielder: "I knew he was going to be aggressive, so I was just trying to stay aggressive also. That was awesome. Earlier in the year, that's how we were playing. We still stayed in it no matter who was out there."
For his part, Iguchi, speaking through an interpreter, gave credit to Hart on the catch.
"I was praying as I was running to the base," he said. "It's just really unfortunate that he caught it."
Brewers starter Dave Bush gave up eight hits, three walks and five runs in five innings.
Ryan Braun homered in the first for Milwaukee, but the Phillies scored three times in the second to make it 3-1. Howard led off the inning his major-league best 19th homer on the road. Aaron Rowand followed with a walk, and Burrell homered to make it 3-1 and extend his hitting streak to 13 games.
"I'd have a hard time thinking back this year for a more exciting win," Brewers manager Ned Yost said. "The fans were into it. Our guys were staying after it. They had a lot of fire in their eyes even when they were down 5-1. You had a good feeling, and it's hard to have a good feeling when Cole Hamels is on the mound."
- Prior to the game, the Brewers activated RHP Scott Linebrink from the bereavement list and designated RHP Elmer Dessens for assignment. Linebrink pitched a perfect seventh, his third appearance for the Brewers since being acquired in a July 25 trade with the San Diego Padres.
- Saturday's crowd of 42,126, the team's 23rd sellout of the season, pushed the Brewers past the 2 million mark in attendance (2,019,799) for just the sixth time, and second-fastest, in franchise history.