MILWAUKEE -- Matt Garza pitched what might have been his best game of the season Friday and certainly one of his best in quite some time, but walked away with little to show for it.

Jordy Mercer's grand slam brought Garza's day to an abrupt end and sent the Pittsburgh Pirates to a 5-3 victory over the Milwaukee Brewers at Miller Park.

Garza cruised through his first five innings and was challenged only once when he faced the bases loaded with two outs in the third, but was doomed by a pair of errors by Jonathan Villar and an intentional walk that set up Mercer's blast in the sixth.

Andrew McCutchen opened the inning by reaching on an throwing error by Villar and Gregory Polanco was safe at first when another Villar couldn't pick up a potential double play ball, putting runners at the corners with nobody out.

"I think the first one was just kind of a routine play he just missed," Counsell said. "The second one was the start of a great double play but he didn't get a good grip on the ball. The second one, that's just a tough play."

After Starling Marte doubled home McCutchen, Garza finally got an out when David Freese struck out. Garza intentionally walked Francisco Cervelli to load the bases for Mercer, who took an 0-2 slider at the knees to left center for his 10th home run of the season and first career grand slam, chasing Garza.

"It was a big pitch, (a) big situation," Garza said. "We walked a guy ahead of the guy to get to who we wanted, I floated a slider in there, and front-footed it and hit a jet stream.

"It's one of those where it's going to suck for a while. I felt like I threw the ball really well. Like I said it's going to suck for a while, it's going to sting, but forget about it and get ready for the next start."

"When you're down 0-2, you just try go into battle mode and try get the job done, get the run in somehow," Mercer said. "(I) was able to get underneath it and put it up in the air and that's what I was wanting to do. Just got enough of it to get it over."

The Brewers picked Garza up in the bottom of the inning, cutting the deficit to 5-3 on a three-run homer by Orlando Arcia, the first of his major league career.

But Milwaukee was stymied by Pittsburgh starter Ryan Vogelsong, who worked 5 1/3 innings in his fifth start since coming off the disabled list and allowed two runs, four hits and four walks.

"I've always been a guy that gets out of stuff, sometimes better than others," Vogelsong said. "But throughout my career, I can probably count how many games I've been pretty clean and go out and keep guys off base. Most of the time, get some traffic and make pitches and get out of it.

"Tonight was one of those nights where I made pitches when I needed to, but overall wasn't really happy with the whole body of work."

The Brewers had their chances against him, putting two out in the second and loading the bases in the fourth but couldn't come up with the big hit.

"We got back into it," Counsell said. "Had a couple of rallies and opportunities but couldn't get that next hit."

Milwaukee challenged one more time in the ninth, bringing the potential winning run to the plate in Domingo Santana, who popped out as Tony Watson earned his ninth save of the season.

NOTES: Pittsburgh manager Clint Hurdle said he had not yet set his rotation for the upcoming series against the Cubs in Chicago. ... Pirates RHP Tyler Glasnow is scheduled to make another minor league rehab start Saturday for Double-A Altoona where he will join C Chris Stewart, who has been out with a left knee injury since July 2. ... Brewers RHP Jacob Barnes was in Triple-A Colorado Springs Friday to start his minor league rehab assignment. ... Milwaukee relievers have allowed only two earned runs in their last 24 innings covering six games. ... Pittsburgh, which snapped a nine-game losing streak to the Brewers on Thursday, is 19-64 in Milwaukee since the start of 2007 and 58-103 overall against Milwaukee during that stretch.