Vargas completed a successful simulated start Tuesday.
"He wasn't tired at all after 60 pitches the other day," Yost said.
Vargas (8-4, 3.31 ERA) last pitched July 8. Two days later, he had his appendix removed and was placed on the disabled list.
Jackson Alexander is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.