Boston strained its already overused bullpen in Thursday's game, as manager John Farrell needed to use five relievers in the 13-inning contest.
De La Rosa, obtained in last summer's big trade with the Dodgers, gives the Red Sox someone who can throw for a longer time if needed.
"[He] can give us multiple innings in the event that something unforeseen happens early in the game," Farrell said before Friday's game. "He's stretched out to 75, 80 [pitches]. He was the most fresh one on the roster that we could go and tap into to add to a bullpen that obviously has been taxed of late."
De La Rosa had a 0-1 record and 3.29 ERA at Pawtucket. He pitched 38 1/3 innings in 11 games, all starts, and held opponents to a .188 average in those games. But now he'll be pitching out of the bullpen.
De La Rosa appeared in 14 Major League games with the Dodgers -- 10 starts -- and has a 4-5 record. He has worked with Pedro Martinez to find more success at this level.
"I'm so excited," De La Rosa said. "I can't wait for tonight. I think I can do it."
Jeff Seidel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.