First baseman Lyle Overbay, whom the Braves signed to a Minor League contract Aug. 20, will be among the first group of callups. He is 6-for-22 with three doubles and six walks in seven games for Gwinnett.
Wren said Overbay "looks like the same guy" as he has throughout his 12-year Major League career.
"He's done well," Wren said. "Good professional at-bats, hitting balls in gaps, all the things he normally does."
Right-hander Peter Moylan will also be in the first group. After undergoing shoulder surgery last October, Moylan signed a Minor League contract and has been working his way back. He pitched in 12 games at Triple-A Gwinnett in August, striking out 13 in 12 2/3 innings.
Moylan tweeted Friday night, "I can't thank the @braves enough for yet another opportunity to compete at the highest level. So excited for tomorrow. #BravesCountry"
Also expected to join the Braves on Saturday will be utility player Jeff Baker, who was acquired Friday night in a trade with the Tigers. Midnight on Friday was the deadline to add players from outside the organization who will be eligible for the postseason.