Providing there are no hiccups for Pomeranz in what is expected to be a five- or six-inning stint, he will start for the Red Sox next weekend against the Orioles on either Friday or Saturday.
Hector Velazquez and Brian Johnson, who filled in for Rodriguez and Pomeranz the first turn through the rotation, will move to the bullpen. The Red Sox optioned right-handed reliever Marcus Walden, who had appeared in three games, to Triple-A as the corresponding roster move for Rodriguez.
Rodriguez underwent right knee surgery in the offseason and had a strong Spring Training, making it back to the Red Sox a little ahead of schedule.
"He's a lot more confident right now than when I met him and talked to him in Miami in late November, early December," Red Sox manager Alex Cora said. "At that point, honestly, I was like, 'This is going to take a while.' In January, he did everything, showed up to Fort Myers [Fla.] early. He worked hard."
Through the first eight games of the season, Boston starters posted an 1.28 ERA.
"It's been exciting watching everybody go out there and just pitch and do their job and be the best they can be," Rodriguez said. "That makes me excited to go out there and try to do the same thing, too, tomorrow."
Pomeranz won a career-high 17 games last season but sustained a mild flexor strain in his left forearm in the second inning of his first start in Spring Training. He joins Chris Sale, David Price and Rodriguez in giving the Red Sox the best collection of lefty starters in the big leagues.