Baker was signed on April 3 after being released by the Yankees at the end of Spring Training. He is 66-52 with a 4.25 ERA in nine MLB seasons.
With Hyun-Jin Ryu still rehabbing from a shoulder impingement, Dodgers management has handled fifth-starter candidates as interchangeable. The club has used David Huff (four runs in four innings) and Mike Bolsinger (one run in 5 2/3 innings).
Baker is coming off a seven-inning shutout victory for Triple-A Oklahoma City on Monday. Triple-A candidates still looking for a shot at starting for the Dodgers are Joe Wieland, Carlos Frias and Zach Lee.
Peralta, who leads the club with three saves, said he has weakness in the right shoulder that he believes is related to upper back spasms he experienced last week.
Manager Don Mattingly compared his level of concern over Peralta to that for Yasiel Puig, who has a nagging left hamstring strain.
"We're not concerned for the long haul," Mattingly said. "They're trying to get rid of stuff. If it's more serious than that, we don't know. We're trying to give him a few days."
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.