CINCINNATI -- Todd Frazier doubled in the 10th inning Sunday, and he was fairly certain teammate Chris Heisey would score from first on the hit.

Even so, Frazier figured he would offer an assist to third base coach Steve Smith, just in case.

"I was waving him in all the way. I touched first and I was still waving him," said Frazier, the Cincinnati Reds' third baseman. "There was no doubt in my mind that he would score. He's pretty fast."

Frazier's hit down the left field line with two outs in the 10th drove home Heisey with the winning run, lifting Cincinnati to a 4-3 victory over the first-place Milwaukee Brewers in the finale of a four-game series at Great American Ball Park.

"When you get those opportunities like that, you want to perform," Frazier said. "I've been getting a lot of them, fortunately for me. It's a lot of fun when you do your job well."

Catcher Brayan Pena and second baseman Brandon Phillips homered for Cincinnati, which took three of four in the series. It was the first road series loss this season for the Brewers.

Second baseman Scooter Gennett and left fielder Khris Davis homered for Milwaukee, which owns baseball's best record (21-11) but concluded a seven-game road trip Sunday with a 3-4 record.

"This would've been an important game to win," Milwaukee manager Ron Roenicke said. "You lose it and it's a bad road trip. You win it and it turns into a good trip. You wouldn't think one game would do that, but it does."

Left-hander Tyler Thornburg (3-1), who walked Heisey ahead of Frazier's double, took the loss. Right-hander Sam LeCure (1-1) earned the victory by pitching a scoreless top of the 10th.

Brewers starter Kyle Lohse, who spent two seasons in Cincinnati, held his former team to two runs and eight hits in 6 1/3 innings. He walked one and struck out two.

"It was a weird outing for me," Lohse said. "At first, (Reds batters) were super aggressive. I tried to used that, and they starting taking. They made me work for the outs that I got."

Reds starter Alfredo Simon, who was filling Mat Latos' spot in the rotation, didn't have his best command, but he gave the Reds a chance to rally. He allowed three runs and five hits in seven innings, walked one and did not strike out a batter. His previous low for strikeouts this season was three.

Gennett started the scoring with a solo home run, his second, to right field in the first inning.

Milwaukee doubled the margin in the third on a two-out RBI single by catcher Jonathan Lucroy. Gomez, who doubled, scored to put the Brewers ahead 2-0.

Pena got a run back for Cincinnati when he launched his fourth home run 456 feet to right field on the first pitch from Lohse in the third, cutting the Reds' deficit to 2-1.

Davis' fourth home run gave the Brewers a 3-1 lead in the fourth.

In the bottom half, Phillips doubled and later scored on Frazier's sacrifice fly to make the score 3-2.

Phillips' first home run since April 5 came off right-hander Brandon Kintzler and tied the score 3-3 in the eighth.

Cincinnati had runners on second and third with two outs in the ninth, but left-hander Zach Duke fanned Skip Schumaker to end the inning.

Milwaukee stranded runners at second and third in the 10th, a continuation of a trend for its struggling offense.

"They did a better job than we did offensively," Roenicke said. "We've got to do a better job of battling. If it makes sense to shuffle, we'll shuffle. But I don't see where there are pieces to make those changes. We get opportunities and we're not getting the job done right now.

NOTES: Reds RF Jay Bruce was scratched from the starting lineup due to left knee soreness. Chris Heisey replaced him and went 1-for-4 with a walk. Bruce pinch-hit in the seventh and struck out. ... Cincinnati C Brayan Pena left the game with a leg injury in the seventh. ... The Reds begin two-game series against the Boston Red Sox on Tuesday at Fenway Park. "They're the world champs, that's a big enough problem," Reds manager Bryan Price said. "They're very, very good." ... The Brewers return to Miller Park for a nine-game homestand beginning Monday against the Arizona Diamondbacks. ... Reds CF Billy Hamilton was out of the lineup for a third consecutive game with sprained knuckles suffered while making a diving catch in the first inning of Thursday's game. He appeared in Sunday's game as a pinch runner. ... Cincinnati's Flying Pig Marathon was held Sunday morning with approximately 20,000 participants hoping to cross the finish line just outside Great American Ball Park.