Mortensen, acquired in the Matt Holliday trade, was recalled from Sacramento to pitch Saturday's game against Kansas City. He allowed eight runs and eight hits with three walks in four innings in the 12-6 loss, his first start in the majors.
Mortensen was 0-1 with a 12.86 ERA in two appearances.
Marshall was 5-3 with a 3.20 ERA and seven saves at Sacramento. He's back in the majors for the first time since 2007.