Podsednik, an All-Star in 2005, was acquired by the Dodgers on Wednesday from the Kansas City Royals for two minor league players.
"With Reed and Manny out, it's tough to tell when they'll be back or if there will be more issues the rest of the season," said Colletti. "This is a safeguard. Podsednik knows how to win and he can help us in a number of ways."
Ramirez is on the disabled list with a strained right calf muscle and is not expected back for several weeks. Johnson has chronic back spasms.
Podsednik, 34, can play all three outfield positions. He hit .310 in 94 games with the Royals and stole 30 bases.
(Reporting by Gene Cherry in Raleigh, North Carolina. Editing by Julian Linden.)