"Especially how the score ended up, I was happy to kind of help the team win on that one," Thames said. "But pitching was also good for us."
Reds starter Sal Romano (0-2) had a two-hit shutout going before Lorenzo Cain walked to open the sixth and Thames sent the first pitch he saw over the wall in right for his team-leading sixth home run. Thames was back in the lineup after leaving Sunday's game with a left groin strain and sitting Monday.
Guerra issued consecutive one-out walks in the first but then limited Cincinnati to a single and another walk over 5 2/3 innings, striking out seven. Dan Jennings (2-0) finished up the sixth, Jeremy Jeffress retired three straight in the seventh and Josh Hader pitched the final two innings for his second save despite allowing a two-out double in the ninth to Tucker Barnhart.
"I don't think he came out of the chute with his best stuff," Brewers manager Craig Counsell said of Guerra. "But he put it together and then got on a roll. I think Junior, when he gets it going, it's pretty darn good."
Romano allowed two runs and four hits in five-plus innings, striking out four and walking two.
"Shoot, he gave us five innings of two-run baseball," manager Bryan Price said. "We just weren't in a position at that point in time to give up any more."
Outfielder Christian Yelich was activated from the 10-day disabled list after recovering from a strained right oblique, and right-handed reliever Jorge Lopez was optioned to Triple-A Colorado Springs of the Pacific Coast League.
Yelich was available off the bench Tuesday night but did not play. Counsell said Yelich probably will start in Wednesday's series finale.
"Getting Christian back is really important," Counsell said. "Yesterday was a day when we probably had four guys out of the lineup that were in our planned lineup for the first day. But that's a baseball season. It's going to happen."
Yelich, acquired in an offseason trade with Miami, hit 39 homers during the past two seasons with the Marlins. He hit .385 with one homer and five RBI this season before going on the DL.
Reds right-hander Ariel Hernandez, who appeared in three games at Double-A Pensacola this season, was traded to the Los Angeles Dodgers for two minor leaguers -- pitcher Zach Neal and 1B Ibandel Isabel. Hernandez made 19 relief appearances in four stints with the Reds last season with a 5.18 ERA.
The Brewers claimed RHP Alec Asher off waivers from the Los Angeles Dodgers and sent him to Triple-A Colorado Springs. Asher was 2-5 with a 5.25 ERA in 24 games with Baltimore last season. He was claimed by the Dodgers in April and made one start at Triple-A.
Reds: C Devin Mesoraco left in the sixth inning with a bruised right wrist. X-rays were negative, the team announced. "We'll see how he is tomorrow, if there's some things he can do for us off the bench," Price said. "I think he'll be able to catch and do whatever he needs back there but we'll see how he can handle the bat." ... OF Scott Schebler (right ulnar nerve contusion) was scheduled to play a second straight rehab game for Double-A Pensacola and could be activated Wednesday. ... RHP David Hernandez (right shoulder inflammation) threw 25 pitches in a simulated game.
Brewers: Veteran LHP Wade Miley was added to the roster at Double-A Biloxi. Miley signed as a minor league free agent in the offseason and injured his groin late in spring training. ... LHP Logan Boone, on the 10-day DL (left triceps), probably will throw a bullpen session sometime this week.
Reds: RHP Tyler Mahle (1-2, 5.63) makes his fourth start in the series finale Wednesday. After allowing one hit over six scoreless innings for the victory in his first start, he has given up 10 runs in 10 innings in his last two outings.
Brewers: RHP Zach Davies (0-2, 6.75) has allowed 12 earned runs in 16 innings in his first three starts. He gave up five runs and seven hits in 4 1/3 in his last start, a 6-5 loss to the Mets.
More AP baseball: https://apnews.com/tag/MLBbaseball
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