Prince Fielder tied a franchise record with his 45th home run. His two-run shot to straightaway center field came in the fourth inning off Reds starter Tom Shearn (3-0), a 30-year-old rookie right-hander making his fourth big league start after 12 years in the Minors.
The Brewers tacked on a run in the seventh inning to pull to 5-3, and Mike Rivera, a late entry to the game at catcher, hit a two-out, two-run home run in the ninth inning to make it 6-5. But Reds reliever Bill Bray retired Kevin Mench for the final out and notched his first save of the season.
Milwaukee's third loss in its last four games was a costly one. The Cubs won in St. Louis and extended their division lead over the second-place Brewers to 1 1/2 games. The Cardinals fell six games out of first place.
"If you want to be there in the end, you have to step up your stuff, step up your game," said Fielder, who was asked if the pressure is starting to mount. "I don't have any pressure. For me, no. I'm actually having fun. This is why you play. So for me there's no pressure, and hopefully it's the same for everybody else."
Fielder tied the club record set in 1979 by Gorman Thomas and matched in 2001 and 2003 by Richie Sexson. He leads the NL in homers.
Shearn was spotted a 5-0 lead by the end of the second inning and made it stand, limiting the Brewers to three runs on four hits over 6 2/3 innings. He was lifted for a reliever with two outs in the seventh inning, just after Brewers starting catcher Johnny Estrada hit an RBI single that cut the deficit to two runs.
That hit came moments after Geoff Jenkins was ejected by third base umpire John Hirshbeck, who had just called the Brewers left fielder out on a check-swing strike.
Jenkins dropped his bat and was promptly ejected.
"I didn't even know I got thrown [out]," Jenkins said. "I was walking back to the dugout. I felt like it was not warranted. I'm not the umpire.
"I thought it was actually comical, if anything," he added.
The Reds got a key insurance run in the eighth inning against September callup Mitch Stetter, but did most of their damage in the first two innings, running wild against Sheets and Estrada. Reds runners stole four bases in an inning for the first time since 1993 during a four-run first, then tacked on another in the second inning against Sheets, who had won eight of his previous nine decisions. After a double steal left runners at second and third base in the first inning, Brandon Phillips put Cincinnati on the board with a two-run single and Adam Dunn followed with a two-run home run.
Cincinnati leadoff hitter Norris Hopper stole his second base of the game in the second inning -- the 34th consecutive steal against Estrada since June 22 -- and later scored on Phillips' sacrifice fly for a 5-0 lead.
Yost pointed to Sheets' slow move to the plate, not Estrada's arm, for the Reds' early-inning track meet.
"Johnny made a couple of nice throws," Yost said. "It's mostly Benny. ... Benny is a little slow to the plate and those guys [the Reds] are very, very quick. They get great jumps and great reads. They're tough to throw out."
The Reds entered the day ranked eighth in the NL in stolen bases. Estrada has thrown out six of 76 basestealers this season (7.9 percent) and backup Damian Miller has thrown out eight of 24 (33 percent).
But the Brewers' early trouble had much less to do with stolen bases than with command issues for Sheets, who surrendered five earned runs and six hits. Yost and Sheets both insisted there were no physical setbacks -- he missed six weeks this season with a finger injury -- making it the shortest start of his career not related to an injury. He pitched 2 1/3 innings against the Astros last May 2 and insisted afterward that he was healthy, but then missed about seven weeks with a shoulder injury.
Sheets had been pulled early from a number of other games before three innings because of injuries ranging from his back, pectoral, rotator cuff, groin and finger. He was also ejected from a game in the top of the third inning on April 17, 2002, after hitting then-Pirates infielder Aramis Ramirez with a pitch that preceded a benches-clearing brawl.
Friday matched his shortest start of the season. Sheets exited after three innings of work at Chicago on April 25 after he tweaked his groin.
"They jumped on me early," he said. "Four runs in the first pretty much doomed my chance of getting deep into the game and put us in a bind."
He believes better outings are ahead.
"I made an adjustment in my last bullpen that I thought was going to be really good, and I still think it is," Sheets said, referring to his between-starts work with pitching coach Mike Maddux. "After the first pitch, I was in the stretch for the whole time. The stolen bases make it kind of difficult, especially when you're letting speed guys get on."