Rookie left-hander Mike Dunn was optioned to Triple-A Gwinnett after recording two outs in Thursday's 6-2 loss to the Washington Nationals.
O'Flaherty is 3-1 with a 2.30 ERA in 41 games. He has missed 34 games since he was placed on the disabled list July 10.
The Braves also are sending infielder Brandon Hicks back to Gwinnett to clear a spot for first baseman Derrek Lee. Lee, acquired from the Cubs on Wednesday for three minor-league pitchers, will join the team in Chicago on Friday.
Hicks was recalled from Gwinnett on Wednesday when first baseman Troy Glaus was placed on the 15-day disabled list with a sore left knee.