Oakland's pitching plans are starting to take shape.

All-Star Bartolo Colon (groin) threw a 38-pitch bullpen session Monday and appears a likely option to start Thursday's game; the A's first want to see how he comes out of the Monday throwing session.

Manager Bob Melvin said Colon geared up slowly but during the second half of the session he was throwing harder and he had good movement on his fastball.

Brett Anderson the A's Opening Night starter is likely to come off the disabled list during this series after missing more than four months with a stress fracture in his right foot. It sounds as if he will be working out of the bullpen. It's unclear if the A's will continue to try to stretch out Anderson in order to start while he's in the bullpen.

"I just want to get out there and help the team any way I can" Anderson said. "Just being back here with the team is exciting."

Anderson says he got a little fatigued in his last rehab outing Thursday but thought his stuff was good with the exception of his fastball command. He made some mechanical adjustments Saturday and feels ready to go.

If Colon cannot start Thursday Anderson is not an option in that spot according to Melvin. It's more likely to be Jarrod Parker though the A's would like to get Parker and Sonny Gray an extra day of rest this week or it even could be Jesse Chavez.

To make a 40-man roster spot for Daric Barton the A's designated Pat Neshek for assignment and called up right-hander Evan Scribner to take Neshek's spot. Neshek had thrown 44 pitches Sunday at Baltimore and the A's needed to make sure they had some fresh arms in the bullpen for the series at Detroit.