Mets manager Terry Collins had a tough decision to make in the seventh inning of a tie game: Stick with R.A. Dickey and let him bat with runners on base or pinch-hit for him and turn the ball over to the bullpen.

He went for the lead, and he regretted it.

Willie Harris flied out as a pinch-hitter to end that chance, then the Brewers took advantage of one of the major leagues' worst relief corps and went on to a 6-2 victory Sunday that completed Milwaukee's first series sweep in New York.

"I should've stayed with R.A," Collins said. "I thought we'd play to win there. We just can't stop anybody."

Prince Fielder drove in the go-ahead run on a botched potential double-play grounder in the eighth, Casey McGehee homered off Dickey and Ryan Braun had three hits, an RBI and scored twice after stealing bases for the Brewers.

Yovani Gallardo and Dickey each pitched seven superb innings but the Brewers' Francisco Rodriguez and LaTroy Hawkins shut down the Mets with two perfect innings. Manny Acosta (1-1), Jason Isringhausen and Tim Byrdak and Pedro Beato couldn't do the same for New York.

Milwaukee won three straight in Queens to send the Mets six games under .500 for the first time since May 4 with a thorough display of superior baseball this weekend. Shaun Marcum stifled New York on Friday in a 6-1 win. Fielder and the Brewers rallied Saturday after blowing a late six-run lead for an 11-9 victory, and Gallardo (14-8) gave up six hits in the finale to match a career high for wins.

The Mets have lost nine of 11 and have struggled on offense since trading Carlos Beltran and having Jose Reyes, Ike Davis and Daniel Murphy out with injuries.

"We're not mounting much of an offense, we're not stopping them on the defensive side," Collins said. "It's pretty tough right now."

The NL Central-leading Brewers have won eight of nine on the road to improve to 29-36 away from home and are winners in 22 of 25 overall. Should the Cardinals lose the Cubs on Sunday night, Milwaukee's fans will wake Monday morning to see its club with the biggest division lead in franchise history, 9½ games.

"We're playing like we do at home," manager Ron Roenicke said of Milwaukee, which is a major league-best 47-16 at Miller Park.

Lucas Duda stunned Gallardo in the seventh after striking out his first two at-bats, launching a home run that landed in the bullpen in right-center to tie it 2-all. But the Brewers rallied in the eighth after Dickey left and the burly Fielder was at the center again.

Fielder had quite a series against the Mets, driving in eight runs. He hit a tying single Saturday in the ninth, then put Milwaukee up 2-0 with a single in the sixth Sunday.

With runners on first and third and lefty Byrdak on the mound in relief of Acosta, Fielder hit a routine grounder to rookie second baseman Justin Turner. But Turner's throw to shortstop Ruben Tejada covering the base was low for an error. Nyjer Morgan, who had walked for just the ninth time this year, scored and Braun — he singled — advanced to second.

"When you play a team like this you know you have to play mistake-free baseball," Mets third baseman David Wright said.

Braun stole third and scored on Jerry Hairston Jr.'s single for a 4-2 lead.

Acosta gave up a hit and a walk in the eighth without getting an out. He failed in the ninth Saturday, coming in with the bases loaded.

The Brewers scored two more in the ninth against a Mets bullpen that has yielded at least one run in 21 of the past 26 games, including four — one unearned — Sunday. New York's relievers have a 5.95 ERA over that span and six losses.

Asked afterward if the bullpen's struggles make it hard to trust the relievers, Collins said: "Sure does."

Morgan bunted with runners on first and third, and Beato had one play: to first as a run scored. Braun laced a run-scoring double to right field for a 6-2 lead.

Gallardo struck out six and walked one intentionally. The homer to Duda was his 18th allowed this season.

Dickey was equally as good. His one big mistake came to McGehee, otherwise his knuckleball confused the potent lineup.

"His knuckleball was great," catcher Josh Thole said. "It was one of the best," this year.

He gave up six hits and two runs without walking a batter. He lasted at least six innings for the ninth straight start.

NOTES: Mets SS Jose Reyes ran from home to first several times to test his hamstring. He will not come off the DL when eligible Tuesday. He will ramp up his rehab Monday by making turns on the bases and increasing the intensity of his workouts. Reyes will likely play in rehab games at the end of the week. ... The Mets travel to Philadelphia where Jonathon Niese (11-10) will face Cliff Lee (13-7).