Capuano was informed of the decision during batting practice on Saturday. Sheets, who strained his left hamstring on Tuesday against the Astros, played light catch with head athletic trainer Roger Caplinger for about five minutes, then walked over, grabbing the back of his left leg.
Manager Ned Yost had a pair of former starters working long relief, but he chose Capuano over right-hander Claudio Vargas because the Braves are 29-32 against left-handed starters and Capuano has a 3.60 career ERA against them.
"He's strong and ready to go," Yost said of Capuano.
The team was not going to take any chances with Sheets. Even though the hamstring in question is not in Sheets' drive leg, doctors advised that putting pressure on it could cause a more serious tear.
Whether Sheets will pitch again in the regular season remains unclear. His next scheduled start is Sept. 28 against the Padres, and Yost intends to stick with that plan.
The alternative is using Sheets earlier in the week, possibly getting him two more regular-season starts instead of just one. The Brewers and Cubs both won on Friday night, but the Brewers fell to two games behind first-place Chicago in the National League Central with the Cubs' Saturday afternoon victory at Wrigley Field.
"You can out-think it," Yost said. "'Just play it' is my thinking. We're going to need all of our starters, anyway."
The fact that the club had Capuano and Vargas waiting in the wings was a plus. Last season, the Brewers crumbled after Sheets and Tomo Ohka suffered injuries in early May, and they ran through a myriad of replacements before finding a semblance of stability with Carlos Villanueva and Zach Jackson.
"It speaks to the value of depth," assistant general manager Gord Ash said. "These options far outweigh what they did a year ago."
It also helps that other Brewers starters, including Villanueva, Saturday starter Yovani Gallardo and veteran Jeff Suppan had been pitching well. Entering Gallardo's outing against the Braves, Brewers starters had produced quality starts -- six or more innings with three or fewer runs -- in six of the last seven games, posting a 2.01 ERA. The only exception was the game in which Sheets had to exit in the second inning with his injury.
The Brewers bestow an "unsung hero" award each season, and there could be quite a debate this year about who deserves it.
On one hand, they have Villanueva, who was surprisingly effective earlier in the year after a switch to the bullpen and now has come back as a starter with some strong performances, including six sharp innings against the Braves on Friday night.
"For me, over the whole year, he's been our pitcher of the year," outfielder Bill Hall said. "Villanueva has helped us in so many different ways."
On the other hand, they have outfielder Corey Hart, who always seems to lurk in the shadows behind other young Brewers, a list that includes Prince Fielder, Ryan Braun, J.J. Hardy and Rickie Weeks.
"I don't think people give him enough credit," Fielder said of Hart. "How many 20-20 guys have been on the Brewers? Let's be honest -- I think [Hart] is awesome. To be that big and that fast with that power is a great asset.
"He doesn't play with fear. That's all you can ask for."
Hart is the fifth Brewers hitter to amass 20 home runs and 20 stolen bases and the first since Marquis Grissom in 1999. He entered Saturday batting .301 with 21 homers, 22 steals and 73 RBIs, and he was batting .419 over his last 28 games.
Hart also ranked fourth in the NL with a .359 average with runners in scoring position, trailing Florida's Miguel Cabrera (.372), Cincinnati's Edwin Encarnacion (.361) and Chicago's Derrek Lee (.360).
"He's played great outfield, he's been a run producer, he's been a leadoff hitter," Yost said. "He's been an offensive catalyst for our team."
The Brewers' home game against the Padres next Saturday, Sept. 29, was moved up to a 2:55 p.m. CT start to accommodate a national FOX television broadcast. The first pitch was originally scheduled for 6:05 p.m. CT.
The game will air locally on WITI-TV, Channel 6 in Milwaukee.
Capuano (5-12, 5.21 ERA) will match up against Braves left-hander Jo-Jo Reyes (1-2, 6.98 ERA), a rookie who has never faced the Brewers. Because of a conflict with a Green Bay Packers game, the Brewers game can be heard in Milwaukee on WSSP-AM 1250. It will be televised as usual by FSN Wisconsin.