Fiers (6-4) has a 1.03 ERA in his last nine starts and continued to dominate against the Reds. He retired the first 18 batters before Zack Cozart doubled to open the seventh.
"Whenever a guy has a no-hitter going into the seventh inning, his pitch count is relatively low," Baker said. "It's not like we were chasing a lot of bad balls out of the zone. The main thing is we had a good game pitched against us.
"When you have a good game pitched against you, there's not a whole lot you can do."
Cueto (14-6) lost for the first time in six starts. He pitched seven innings, giving up three runs on six hits while striking out nine. The big hit was a two-run home run by Aramis Ramirez in the first inning.
"Johnny pitched a great game, too, other than the first-inning two-run homer," Baker said. "Not a whole bunch to say. He just beat us tonight."
Cueto said he simply made a bad pitch to Ramirez.
"I'm not perfect," he said through an athletic trainer serving as a translator. "I wanted to throw the ball in a different spot, but I threw the ball in the hitter's spot. It was good for him."
The Reds have lost three consecutive games, the team's longest losing streak since dropping three straight from July 3-5 (two losses to the Dodgers and one to the Padres). Pittsburgh lost to Arizona on Tuesday night, so Cincinnati maintained its 3 1/2-game lead in the National League Central.
"You know that times aren't always going to be good," Baker said. "You're going to get beat sometime. You don't like it, but you realize that those [opponents] guys get paid, too, to play ball."
Before the three-game slide, the Reds had won 22 of 25 games.
"We'll get it together and make another nice run," Baker said. "That's why you run the race, and that's why you play the whole season."
The Reds threatened in the eighth, using a pair of singles by Xavier Paul and Ryan Hanigan to put runners on the corners with two outs. Milwaukee manager Ron Roenicke went to the mound but stuck with Fiers, and he struck out pinch-hitter Ryan Ludwick on his 113th and final pitch to end the threat.
Rookie Jim Henderson pitched the ninth for his first Major League save.
Milwaukee took a 2-0 lead in the first on Ramirez's 15th homer this season.
The Reds got their first hit to open the seventh when Cozart doubled, moved to third on a flyout and scored on Brandon Phillips' sacrifice fly.
Fiers said he threw a cut fastball to Cozart.
"I thought it was a good pitch," Fiers said. "He went out there and got it, got the barrel on it and put it in a good spot."
The Brewers then tacked on another run in the bottom half of the inning on an RBI groundout by Jean Segura, his first Major League RBI, scoring Rickie Weeks from third.
It was the second time Fiers has faced the Reds this summer. The right-hander took the loss in a 2-1 Cincinnati victory on July 22, but gave up only two runs, one earned, in six innings.
"He was basically the same," Baker said of Fiers' two outings against his team.
Baker compared Fiers to San Francisco starter Tim Lincecum.
"He's very deceptive with that Lincecum-type windup he has," he said. "I don't know if he got it from Tim or not, but it's working for him. When a guy comes in with a low ERA like that, he's not only beating you, he's beating everybody in the way.
"You don't want to lose, but tonight he just pitched a great game against us."