Overbay is hitting 2 for 20 (.100) in 10 games with three RBIs. The 37-year-old first baseman is in his second stint with the Brewers after signing with the team in the offseason.
Overbay and his wife, Sarah, are expecting their fifth child. The Brewers begin a four-game series at Pittsburgh on Thursday.
Herrera was hitting .250 with two RBIs at Nashville.