With his return comes an extra day of rest for lefty Brett Anderson, who will now pitch Sunday for his third start of the season, after compiling 14 innings in his first two starts.
Griffin, sidelined by a strained right shoulder since exiting his Aug. 4 start early, essentially takes over the suspended Bartolo Colon's rotation slot. He made two rehab starts with Triple-A Sacramento, his most recent a one-run, five-inning outing.
"I felt like I was holding back a little bit that first outing and maybe thinking about it too much, so my location was off," Griffin said. "I got my location back the second time and am feeling confident."
The rookie was superb for the A's before being sidelined, compiling a 3-0 record and 2.42 ERA in eight starts. He returns to a staff that entered Friday having compiled a 10-2 record and 3.06 ERA over the last 14 games, a stretch that has resulted in a 12-2 team record.
"Obviously it's nice they want me to be back and contributing to this team," Griffin said. "It makes you feel good, like you're valued and they support you."
"It was unfortunate he went down when he did, because he was pitching really consistently for us," manager Bob Melvin said. "I think the dynamic of bringing him back was more about how many starts he would need before coming back. We didn't feel he was ready after the first but we felt he was after the second."