The rookie right-hander is 2-3 with a 4.31 ERA in eight starts. He allowed six runs over 2 2-3 innings Friday night against Minnesota. Anderson had an MRI on Saturday that revealed the strain.
Almonte, acquired from San Diego for left-hander Marc Rzepczynski on July 31, was set to start in center field and bat eighth Saturday night. Almonte hit .204 with four RBIs in 31 games with the Padres.
Armstrong was 1-2 with 14 saves and a 2.25 ERA in 40 relief appearances at Columbus.
Holt went 2 for 20 in nine games with the Indians.