"It's two out of three. That's all it is," Braves manager Bobby Cox said, downplaying the importance of the series.
But the two-time NL championship Phillies now are six games behind Atlanta with their seventh loss in 10 games. It's the furthest they've been out of first place since Sept. 13, 2007 when they were 6 1/2 behind the New York Mets. The Phillies overcame a seven-game deficit with 17 to play to win the first of three straight division titles.
"We're having a tough time right now," Phillies manager Charlie Manuel said. "We're kind of banged-up, but if we're going to compete, we can't be chasing two teams. People say we're a second-half team. I'm not saying we're not, but we don't want to get too far behind."
"We try, but that little spark, that little swagger, just enough cockiness to make you good, something's missing there; that's what we got to get back," Manuel said. "We got to get that edge. Something on our team is missing; it's that edge, that push."
Medlen (6-1) allowed four runs and seven hits in 6 2/3 innings. The Braves are 10-1 in his starts this season.
"I felt great," Medlen said. "I got a lot of run support. That big inning was huge."
Billy Wagner tossed a perfect ninth for his 19th save in 22 chances.
The 47-year-old Moyer allowed seven runs and seven hits in 5 1/3 innings. The soft-tossing lefty failed in his second attempt at reaching 10 wins for the 16th time in his 24-year career.
"There's some new faces in here," Moyer said. "As teams change, there's responsibility among those who remain to carry on that swagger. We just haven't found a way to get going on all cylinders."
Howard put the Phillies ahead 3-1 with an opposite-field, two-run shot in the fifth, but the Braves quickly answered.
Diaz then hit one out to straightaway center to chase Moyer and give the Braves a 7-3 lead.
But Saito retired Juan Castro on a pop-up to strand two runners.
Prado drove Moyer's third pitch into the seats in left for a 1-0 lead and his third career leadoff homer -- all this season.
"We knew Moyer likes to hit his spots," Prado said. "We said to be patient and wait for a good pitch to hit."
Jimmy Rollins hit a two-out RBI double to tie it at 1 in the second.
Atlanta is 14-1-3 in 18 series since losing two of three in Philadelphia in May. ... Prado has both of his career multihomer games this season. ... Braves OF Nate McLouth will begin a rehab assignment on Friday. ... Phillies relievers Chad Durbin and Antonio Bastardo will start their rehab stints on Saturday. ... A crowd of 44,282 was the 80th straight sellout at Citizens Bank Park.