Vargas will be available for Friday night's series opener against the Athletics at Safeco Field.
Acquired from the Mets last December in the three-team, 12-player trade, Vargas got off a blazing start at Tacoma, going 1-1 with a 2.49 ERA in four starts. He has pitched 11 2/3 consecutive scoreless innings, allowing just four hits.
General manager Jack Zduriencik said Vargas would replace Corcoran in the bullpen, giving the Mariners their first left-handed reliever this season.
"He can give you multiple innings," Zduriencik said, "and has pitched out of the bullpen before."
Vargas, who missed all of last season after undergoing surgery in March 2008 to repair the labrum in his left hip, has previous Major League experience with the Marlins in 2005 and '06 and with the Mets in '07. He has a career record of 6-8 with a 5.81 ERA in 31 games, including 20 starts.
Corcoran, the team's Unsung Hero last season after compiling a 6-2 record and 3.22 ERA in 50 relief appearances, has a strained neck and will be sidelined at least until May 14.
The 28-year-old has appeared in eight games this season, posting a 1-0 record and 7.27 ERA, allowing 13 hits, nine walks and seven earned runs in 8 2/3 innings.
The Mariners are expected to activate catcher Kenji Johjima from the 15-day disabled list prior to Friday night's game. It is likely that backup catcher Jamie Burke would be designated for assignment to create a roster spot for Johjima.
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.