The Oakland Athletics suffered setbacks to two rehabbing starters, Jarrod Parker and A.J. Griffin.

Parker left a rehab outing at Triple-A Nashville with a potentially significant elbow injury; observers told The Chronicle that Parker was in “excruciating pain” and close to tears coming off the field.

“You cross your fingers, obviously, for Jarrod. I don’t even know what to say,” A’s manager Bob Melvin said. “For a guy who’s worked as hard as he has to get back, I really don’t have words for that. I just feel really bad for him.”

Griffin, like Parker recovering from Tommy John surgery, was shut down Thursday with shoulder soreness two innings into a three-inning simulated game at extended spring training in Arizona. 

Fans in attendance said that Parker went down in a heap on the mound, clutching his arm. The A’s said in a release that Parker left the game with an elbow injury but there would be no diagnosis until he has seen a doctor.