The Angels recalled Richards from Triple-A before Wednesday's game against the Red Sox. Outfielder Peter Bourjos was placed on the 15-day disabled list with a sore right wrist, retroactive to Aug. 19.
Richards started nine games before he was sent down on Aug. 2, going 3-2 with a 4.42 ERA. For now, the Angels think he can help the bullpen, which has a 5.92 ERA after the All-Star break entering Wednesday's game.
"He still has his length, but we're planning on using him out of the 'pen to see if he can be an effective piece there," Angels manager Mike Scioscia said. "We'll take it one step at a time."
The Angels' rotation has also struggled recently, with a Major League-worst 6.56 ERA in August entering Wednesday. Richards figures to be a middle reliever, but his role could expand if he pitches well.
"He can pitch himself into more of a role in the bullpen," Scioscia said. "We're going to see where our pitching staff is and evaluate it, but right now we have our five guys and hopefully they're going to continue to move forward as Ervin [Santana] has and then see where Garrett's arm plays in our 'pen."
While Richards has made 12 starts in 17 appearances for the Angels the last two years, he's not opposed to going to the bullpen.
"I'm going to do whatever they ask me to do whether it's starting or in the bullpen," Richards said. "I'm just glad to be back."
Bourjos is hitting .227 with three home runs and 19 RBIs in 88 games this year.