CINCINNATI -- Milwaukee Brewers right-hander Jimmy Nelson made adjustments last season with a modified delivery and strengthened his lower body through Pilates workouts over the winter. He is beginning to see results.

Ryan Braun hit a two-run home run, Eric Thames added a solo shot, and Nelson allowed one run and five hits through seven innings, lifting Milwaukee to a 5-1 victory over the Cincinnati Reds on Thursday night in the opener of a four-game series at Great American Ball Park.

"It all starts from the ground up," Nelson said. "The strength and balance of my legs from some of the things I did this offseason really helps. That's where it all starts."

It was the second strong outing this season for Nelson (1-0), who struck out five and did not walk a batter while helping snap the Reds' four-game winning streak.

Nelson gave up one run in six innings but received a no-decision last Friday in Milwaukee's 2-1, 11-inning win over the Cubs.

Limiting walks has been key for Nelson, who has issued just two free passes in two starts.

"A zero in the walk column over seven innings, that's a good sign he's made some improvements and adjustments," Brewers manager Craig Counsell said. "Players make adjustments and sometimes we don't get the results immediately. He's really stuck with this. It was plus stuff the whole night."

Thames went 2-for-3 with two RBIs, and Orlando Arcia had three hits to pace Milwaukee's offense.

Reds shortstop Zack Cozart went 3-for-3 to extend his season-opening hitting streak to nine games. He hit in 10 straight games to begin last season.

Cincinnati right-hander Bronson Arroyo (0-2) made his first start at Great American Ball Park since 2013, but it was a rough homecoming for the veteran, who allowed five runs and seven hits in six innings. Arroyo rejoined the Reds in spring training after not pitching for nearly two full seasons due to elbow and shoulder surgeries.

"I feel like I have less room for error," Arroyo said. "I feel like I don't have enough to finish guys. My (velocity) obviously isn't as good as it used to be. I can get into counts to keep guys off the bases with walks but if I keep giving up big innings like I did the last two times out, it is going to be hard to keep the team in the game."

Reds center fielder Billy Hamilton starred with the bat and glove in the first two innings.

Hamilton helped Arroyo retire the Brewers in order in the first when he hauled in Braun's deep drive to the wall in center to end the inning.

In the second, Hamilton crashed into the right-center-field wall while snaring Domingo Santana's deep fly.

Cincinnati gave Arroyo a lead in the bottom half of the first when Hamilton singled, stole second and later scored the Reds' only run on Joey Votto's sacrifice fly.

"That's what he does, he gets on base," Nelson said. "What you don't want to do in that situation is let the fact that he's on base disturb your delivery and things kind of snowball on you."

Nelson didn't, and Cincinnati failed to get a runner past second base from that point on.

Arroyo retired the first six batters he faced, but Milwaukee broke through for four runs in the third. The big blow was Braun's two-run home run, his third of the season and 36th of his career against Reds pitching to give the Brewers a 4-1 lead.

"Bronson is 2 1/2 years removed from competing," Cincinnati manager Bryan Price said. "He had six Cactus League games, he needs time to settle in. He was better than he was in St. Louis. I thought it was important that he got his innings. That's contributing. It saved us from going to the bullpen earlier. His crispness needs to get better, not necessarily his velocity."

Thames' solo homer to right field in the fifth made the score 5-1, leaving Arroyo to question where he is mechanically after his long absence from the game.

"If the next two times out I don't see something a little crisper to keep us in the ballgame, maybe I'm on a dead-end street," Arroyo said. "I'm not sure."

NOTES: Cincinnati won its first three series to begin a season for the first time since 1990 when they won the World Series. ... Brewers RHP Matt Garza (right groin strain) made his first rehab start for Triple-A Memphis on Wednesday night, allowing one earned run in five innings. He is expected to make one more start. ... Reds RHP Barrett Astin recorded his first career strikeout in the ninth inning. He threw two scoreless innings.