CINCINNATI (AP) -- Milwaukee's impressive bullpen had one very bad inning.
Brayan Pena's second career pinch-homer started Cincinnati's big eighth-inning rally and swept the Reds to an 8-3 victory over the Brewers on Thursday night.
The Reds hit three homers in all as they pulled within 6 1/2 games of the NL Central leaders, who came in with the fourth-best bullpen in the league. The Reds sent 11 batters to the plate while scoring five times in the eighth.
A rare bad day by the relievers.
"They're going to happen, no doubt," manager Ron Roenicke said. "We've been good down there. We just weren't good tonight."
Neither was starter Marco Estrada, who gave up three runs, six hits and four walks in six innings, leaving with the score tied at 3.
"If I'd have made my pitches, we could have won today," Estrada said. "We scored three runs off Homer Bailey and that should have been enough."
Tucker Barnhart led off the fifth with his first career homer. Todd Frazier added a two-run drive in the sixth off Estrada, who had trouble controlling his pitches.
"I left a lot of changeups up," he said. "When I tried to come inside on guys, it wasn't for a strike. It was everything. The curve wasn't that great today.
"I got away with too much today."
Both homer runs came off changeups and barely cleared the walls.
"Both of them were out front," Roenicke said. "The ball carries very well here. I didn't think either one was going to be a home run."
Pena had homered during a 9-4 loss to the Cubs on Wednesday night. He hit for Bailey with the score tied at 3 in the eighth and connected on the first pitch from Jim Henderson (2-1) for a two-run homer that started the winning rally.
Bailey (2-2) allowed eight hits in a season-high eight innings, finally returning to form after missing much of spring training with a strained groin.
Milwaukee has lost back-to-back games for only the second time this season. The Brewers haven't dropped more than two in a row.
Cincinnati opened the four-game series with another injury. Leadoff hitter Billy Hamilton sprained knuckles on his left hand while making a diving catch in center field and will miss a few games.
Hamilton stretched all out to reach Carlos Gomez's line drive that opened the game. He grimaced and flexed his left hand and wrist as he got up. Chris Heisey hit for him in the bottom of the inning.
Gomez stole a hit from Joey Votto in the bottom of the first, catching his fly at the top of the wall in center. Votto pointed two fingers toward Gomez, who also stole a potential go-ahead homer from him for the final out in Milwaukee's 4-3 win last July 8.
Jean Segura singled in a run in the second, and Gomez doubled home a pair of two-out runs to tie it 3-all in the seventh.
Milwaukee got two players back in the lineup, but outfielder Ryan Braun missed his fifth game because of a strained oblique. Braun is expected back this weekend.
Segura returned at shortstop after being out of the starting lineup for four games because of an injury to his face. Third baseman Aramis Ramirez was back after missing two games with a sore left elbow and went hitless, extending his slump to 0 for 25.
Outfielder Logan Schafer is eligible to return from the disabled list on Saturday, recovered from a strained right hamstring. For now, Roenicke is using Mark Reynolds in right field, a position the infielder played during spring training.
NOTES: RHP Wily Peralta (3-1) faces RH Mike Leake (2-2) in the second game of the series. ... The Brewers called reliever Rob Wooten. Milwaukee's bullpen has thrown the fifth-most innings in the majors. Utility player Elian Herrera was optioned to Triple-A. ... The Reds put LHP Tony Cingrani on the DL with a sore pitching shoulder. Reliever Curtis Partch was called up from Triple-A. ... Closer Aroldis Chapman made his first rehab appearance, throwing one inning and fanning two batters at Class A Dayton. He's recovering from a line drive off the forehead on March 19. He could be activated by the end of next week.