Marshall, 26, was 0-2 with a 14.72 ERA in 10 outings out of the Oakland bullpen following his Aug. 9 promotion to the Majors, but had been one of Triple-A Sacramento's more effective relievers prior to that, going 5-3 with seven saves and a 3.20 ERA in 50 games with the River Cats.
Originally drafted by the Chicago White Sox in the 25th round of the 2002 First-Year Player Draft, Marshall made his big league debut with Oakland in 2007 as a Rule 5 selection, spending the entire season with the Athletics and posting a 6.43 ERA in 51 games.
In 61 big league games, he has a 7.66 ERA, with a 2.85 ERA in 219 Minor League games.
Lisa Winston is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.