MILWAUKEE — For a few moments after five innings Saturday afternoon, Milwaukee Brewers catcher Mike Rivera found himself thinking back to that hot night last June in Round Rock, Texas, when he was on the receiving end of left-hander Manny Parra's perfect game for Class AAA Nashville.

"It was like a flashback going through the fifth with no hits," Rivera recalled.

That flashback came to an abrupt end on the first pitch of the sixth inning, a high and outside offering that San Francisco left fielder Eugenio Velez lined into the right-field corner for the Giants' first hit of the game, a triple.

But while Parra would last just three more hitters and give up two runs, it only slightly tarnished the rookie's first appearance this season as a member of the Brewers' rotation and his first major league win.

Parra went 51⁄3 innings and struck out seven in his season debut, setting up the Brewers' fourth victory in five games, a 5-4 win over the Giants before 30,574 at Miller Park.

"When you first get up here, you want to feel like you're contributing to the team," Parra said of his brief stay with the Brewers last year — a stint that came to an unceremonious end in late August when he fractured his left thumb on a bunt attempt.

"Finally, I feel that way. I feel like I got my job done."

Parra did it in grand style, too, through five innings, working out of error-caused jams in the second and fifth before faltering in the sixth and giving way to David Riske, the first of three Brewers relievers who were able to keep the Giants at bay.

"He was flowing through five, unhittable," Milwaukee manager Ned Yost said.

The last reliever of that trio was Eric Gagne, who made amends for his hiccup last Monday in Chicago by setting down the Giants in order in the ninth for his first save as a Brewer.

"The first one's out of the way," said Gagne, who blew a save opportunity against the Cubs by surrendering a three-run homer in the ninth to Kosuke Fukudome. "I don't believe in the first one getting out of the way should be that hard, but I guess it is a little harder."

Rivera, making his first start of the season, played a key role in building Parra a 3-0 lead.

In the second inning, his 75-foot single in the no-man's land between the mound and third base scored Corey Hart all the way from second, a decision Hart made as soon as third baseman Jose Castillo unwisely tried to get Rivera at first. The throw home from first baseman Dan Ortmeier wasn't even close to being in time to get a sliding Hart.

In the fifth, Rivera followed Hart's double with one of his own just beyond the outstretched glove of center fielder Rajai Davis to give Milwaukee a 2-0 lead. Rivera then showed some Hart-like banditry by tagging up and going to third on Craig Counsell's liner to right, which allowed him to score on Gabe Gross' two-out single.

"You have to know your limits," the slow-footed Rivera said, "but I knew the ball was low and he wasn't going to catch it cleanly, so I went.

"It's contagious," he added about the aggressive baserunning the Brewers have shown through five games. "You see everybody playing hard, so whenever you're out there, you have to be the same way, so even the backup catcher can go from second to third."

The Brewers made it 4-2 in the sixth on Ryan Braun's first home run of the season and 5-3 in the seventh on Gabe Kapler's pinch-hit blast, also his first.

That was enough to make a winner out of Parra, who earned his spot by winning a job with a solid spring training. In the process, Parra is starting to make believers out of many.

"It helps your confidence when you know Ned and your teammates have confidence in you," Parra said. "You want to feel like your teammates have confidence in you. By making this team, they believe in me. So I better believe in myself."