Grilli, 38, was a first-time All-Star last season, but he has a 4.87 earned-run average this season. He has blown four of 15 saves this season and lost his job as closer last week. In his last six appearances, he has given up six runs and 11 hits in 4 2/3 innings.
Angels General Manager Jerry Dipoto said he is not through working on trades to improve the bullpen. The Angels would like to add a veteran late-inning reliever, ideally a left-handed one, and they might still need a closer.
"This is a step," Dipoto said. "I'd be surprised if this is the only step."
While the Angels would like Grilli to establish himself as their closer, they are making him no promises.
"Whether Jason Grilli returns to the ninth inning will have to be determined by Jason Grilli," Dipoto said.
Frieri, 27, saved 70 games for the Angels over the past three seasons, but he was removed from the closer role four times. His ERA rose from 2.32 to 3.80 to 6.39 in that time. In his last appearance with the Angels, he was asked to pitch the ninth inning with a 6-1 lead on Thursday. He gave up three runs, and the Angels were forced to rush Joe Smith into the game.
"We are trading a struggling closer for a struggling closer with the idea that a change of scenery will help both," Dipoto said.
Frieri was not available for comment. Manager Mike Scioscia said he hoped Grilli would join the Angels here Saturday.