J.J. Hardy had a solo homer for the Brewers, who snapped a six-game losing streak against the Phillies in the regular season. Philadelphia beat Milwaukee 3-1 in a first-round playoff series last fall.
"I was just trying to keep the ball down and get ground balls," Looper said. "You get the ball up against that club and they'll make you pay for it."
After striking out Ryan Howard, Coffey allowed a solo homer to Jayson Werth and a single to Raul Ibanez. He retired Pedro Feliz on a fielder's choice grounder before pinch-hitter Matt Stairs singled. Coffey then struck out pinch-hitter Chris Coste to end it.
Phillies starter Joe Blanton (0-2) gave up three runs and eight hits in six innings. He has lost two straight outings after going unbeaten in his first 17 starts with Philadelphia.
"I felt like I threw some decent pitches, some good sinkers and got a lot of ground balls," Blanton said. "I felt like I've been better each time."
Only three runners reached second base against Looper, who lowered his ERA to 2.12. Signed as a free agent to bolster a depleted rotation, Looper has been Milwaukee's best starter this season.
The right-hander escaped his only jam in the sixth after two batters reached with two outs. Ibanez ripped a liner to right, but Corey Hart ran back and made a twisting catch.
Looper hadn't had much success against the Phillies in the past. He entered 2-6 with a 5.53 ERA in 60 career games against Philadelphia.
"He's very intense about his preparation and he's focused on what he has to do," Brewers manager Ken Macha said. "Looper should be a nice model for everybody to follow."
On a chilly, rainy night when strong winds made fly balls adventurous, there wasn't much offense.
Hardy hit a 3-2 pitch into the left-field seats to give Milwaukee a 1-0 lead in the fifth. Cameron lined a two-out double to make it 3-0 an inning later.
Those were all the runs Looper needed.
"It was a little hard to concentrate with the wind and rain," he said. "The ball felt a little slippery."
Prince Fielder reached on an infield single in the second inning when first baseman Howard overran his popup that got caught in the strong wind.
Ryan Braun lined a single off the left-field wall in the fourth and was thrown out trying to stretch it into a double on a perfect throw by Ibanez.
"We hit four balls hard right at the right fielder," Phillies manager Charlie Manuel said. "It seemed if something good happened for us, we didn't take advantage of it."
The Phillies have rescheduled Monday's rainout against San Diego for July 23. ... No Brewers starter has pitched seven innings this season. ... The Phillies had outscored the Brewers 40-15 in their past six meetings. ... Brewers 2B Rickie Weeks returned to the lineup after leaving Tuesday night's game with dizziness. ... Braun hasn't committed an error in 163 games in LF after making 26 errors as a rookie at 3B in 2007.