Storen saved 43 games in 2011 and 29 last year for the Nationals before being traded to Toronto for outfielder Ben Revere. But things never clicked with the Blue Jays as his velocity dropped several miles per hour, though he still struck out 32 batters.
"Obviously, this has not been Drew's best season, but he is closely linked to a run of great success pitching in the back end of very good bullpens," Mariners general manager Jerry Dipoto said. "Hopefully this serves as a change of scenery and over the next two months we can get him back on track."
Benoit has also struggled in Seattle, losing his eighth-inning setup role to hard-throwing Mariners rookie Edwin Diaz. Benoit, who turned 39 on Tuesday, has posted a 5.18 ERA with a 1.44 WHIP in 26 games while dealing at times with a back issue that first cropped up in Spring Training.
The 15-year MLB veteran has been one of baseball's steadiest setup men in prior years and has a career 3.87 ERA and 50 saves in 687 appearances.
Benoit threw a perfect eighth inning against the Blue Jays in Seattle's 2-0 loss at Rogers Centre on Sunday, but gave up three runs on two hits and a walk in two-thirds of an inning in his previous outing against the White Sox on July 19.
Benoit had a 1.96 ERA in 120 games for San Diego in 2014-15. He previously spent eight years with Texas, three with Detroit and one with Tampa Bay.
The Mariners acquired Benoit in an offseason trade from the Padres with the idea that he'd be the setup man to closer Steve Cishek, but Diaz has stepped into that role with a dominating performance in recent weeks as the 22-year-old rookie has a 1.99 ERA and 44 strikeouts with six walks in 22 2/3 innings since being called up in early June.
Greg Johns has covered the Mariners since 1997, and for MLB.com since 2011. Follow him on Twitter @GregJohnsMLB and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.