Berg went 0-1 with a 5.18 ERA in 41 games with the Cubs last season. He will be available for Saturday's game against the Dodgers.
Right-hander Jeff Stevens was sent down to Iowa to make room for Berg. Stevens pitched 3 1/3 innings in Friday's loss, drawing praise from Cubs manager Mike Quade for helping save the bullpen for the rest of the series.
"As tough as [sending a guy down is], when a guy gives himself up like [Stevens] did yesterday for us and gets us through a tough day, it becomes even tougher," Quade said of the reliever who has a 5.14 ERA in seven innings pitched. "It's part of the business and Jeff understands that."
Quade said that Stevens looked like a much improved pitcher from last season and he expects him to eventually be back with the big club and help the team throughout the course of the season.
ESPNChicago.com's Sahadev Sharma contributed to this report. Information from The Associated Press was used in this report.