"His last start was much improved in terms of overall stuff," said Farrell. "There was increased intensity, increased velocity, increased action to his pitches that are going to be required here, and he gets the ball tomorrow."
Doubront was with the team in Oakland on Thursday and will face recent A's acquisition Brad Mills on Friday. The 26-year-old Doubront went 2-4 with a 5.12 ERA in nine starts before going on the DL.
Workman, who was disciplined for throwing a pitch behind Evan Longoria on May 30, began serving his six-game suspension Wednesday after an appeal with Major League Baseball led to no reduction of the penalty.
Since replacing Doubront in the rotation, Workman is 1-0 with a 3.21 ERA in five starts. He will be eligible to return Tuesday.
Aaron Leibowitz is an associate reporter for MLB.com.