Halladay continued the Phillies' pitching dominance in Milwaukee and Ryan Howard homered in his return to the lineup, leading Philadelphia to a 5-3 victory over the Brewers on Friday night.
Halladay (17-5) struck out nine to reach 204 for the season and scattered four hits and a run over eight innings after the Brewers roughed him up in April. Cole Hamels tossed a complete game in Thursday's opener.
"When you got guys like Roy Halladay and Cole Hamels and those type of guys out on the mound with their good stuff and their good location, it's going to be tough. Not saying it can't be done, (it) definitely increases the degree of difficulty a little bit," McGehee said. "You've just got to take advantage of the few mistakes that you get. Hopefully, we get another shot at them down the road."
Elsewhere in the NL, it was: Washington 4 Houston 3 (11 innings); Florida 13 Pittsburgh 4; N.Y. Mets 5 Chicago Cubs 4; St. Louis 4 Atlanta 3 (10 innings); Cincinnati 4 Colorado 1; Arizona 3 San Diego 2; and L.A. Dodgers 2 San Francisco 1.
At Milwaukee, the NL East's top team won its fifth straight and bettered the NL Central-leading Brewers again. Milwaukee scored twice in the ninth after Halladay left, but lost its fourth straight as its lead shrunk to seven games over St. Louis.
"A couple of broken bat hits, a couple of bloopers fall in. You know when things aren't going your way, that happens," Brewers starter Shaun Marcum said.
Also one big hit.
After Shane Victorino singled off Marcum (12-6) to leadoff the game and reached third on Hunter Pence's broken-bat single, Howard turned on a pitch for his 32nd home run, easily reaching the first row of the second deck in right field to give him an NL-leading 108 RBIs this season.
"When you're down 3-0 to Halladay, you're going to have a tough night," Brewers manager Ron Roenicke said.
In the ninth, Prince Fielder singled and McGehee walked with no out against Antonio Bastardo.
Bastardo was pulled for closer Ryan Madson, who allowed a one-out RBI single to Yuniesky Betancourt and a sacrifice fly to Jonathan Lucroy to make it 5-3 before converting his 29th save by getting George Kottaras to ground out.
The Phillies took a 5-0 in the seventh on Raul Ibanez's single that chased Marcum and Carlos Ruiz's single off reliever Takashi Saito. Betancourt's sacrifice fly cut in the seventh gave Milwaukee its only run off Halladay even though it appeared on replay that McGehee never touched home plate.
The Brewers scored six runs off Halladay in a 9-0 win on April 19, but couldn't find similar success against the NL's reigning Cy Young winner in losing for the seventh time in their last 11 games.
Milwaukee squandered its best chance for a big inning in the fourth. The Brewers loaded the bases with one out, but Betancourt swung at the first pitch and grounded into a double play to end the threat.
"We had the bases loaded there with one out," Roenicke said. "That was our shot."
Dodgers 2, Giants 1
At San Francisco, NL Cy Young Award contender Clayton Kershaw outdueled two-time winner Tim Lincecum, pinch-hitter Jamey Carroll drove home the go-ahead run in the ninth and the Dodgers beat the Giants.
Marlins 13, Pirates 4
At Pittsburgh, Omar Infante and Logan Morrison both homered during a nine-run third inning and the Marlins pounded out 22 hits in a rout of the Pirates.
Nationals 4, Astros 3, 11 innings
At Washington, Jimmy Paredes, inserted in the game in the top of the 11th, made a wild throw to second base, allowing Ryan Zimmerman to score the winning run in the Nationals' victory over the Astros.
Mets 5, Cubs 4
At New York, Justin Turner drove in the winning run on a long single with two outs in the ninth inning, giving the Mets a victory over the Cubs.
Reds 4, Rockies 1
At Denver, the Cincinnati Reds took advantage of a poor defensive play by Colorado on Joey Votto's single in the sixth and rallied for four runs to beat the Rockies, ending a 10-game losing streak at Coors Field.
Cardinals 4, Braves 3, 10 innings
At St. Louis, Nick Punto hit a sacrifice fly with the bases loaded in the 10th inning after Albert Pujols' two-run single tied it an inning earlier and the Cardinals kepttheir faint post-season hopes alive with a victory over the Braves.
Diamondbacks 3, Padres 2
At Phoenix, Seldom-used first baseman Lyle Overbay singled in the tiebreaking run in the eighth inning and Daniel Hudson pitched his third complete game of the season, leading the Diamondbacks to a win over the Padres.