BOSTON (AP) -- The Boston Red Sox sent righty David Riske to the Chicago White Sox for lefty Javier Lopez in a trade of relievers Thursday.
The Red Sox bullpen had no lefties and had been struggling recently.
Lopez was 2-1 with an 0.55 ERA with 12 saves for Triple-A Charlotte this year. He was expected to be with Boston for Thursday night's finale of a three-game series at Minnesota.
Lopez appeared in 171 games with Colorado and Arizona and has a 6-4 record with a 6.09 ERA in the majors.
Riske, obtained by Boston in an offseason trade that brought center fielder Coco Crisp to the Red Sox, was 0-1 with a 3.72 ERA in eight appearances. He was on the disabled list with a lower back strain from April 12 through May 22.