The Cubs split a doubleheader against the San Diego Padres on Wednesday and used three relievers in Friday's 12-2 loss to the Los Angeles Dodgers.
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.