Parker suffered the same injury in the past and has undergone two Tommy John surgery procedures.
After appearing set to bounce back this spring, Parker was in a position to compete for a spot in Oakland's bullpen. He left the mound screaming Thursday afternoon, but the hope was Parker was suffering from an elbow injury unrelated to those he has been plagued by in the past.
It might be difficult for Parker to attempt another comeback, since his most recent surgery was last May. The fracture is thought to be an obscure injury that could be difficult to come back from. Parker might have even more difficulty returning to the mound after suffering from the injury a second time.
Arizona drafted Parker ninth overall and he was one of the bigger names to head to Oakland in the deal involving Trevor Cahill.
Parker has only appeared in four minor league contests since the end of 2013. He will enter his final year of arbitration in 2017 before becoming a free agent.
There is a chance Parker returns and has success. But it might not happen quickly and takes an arm away from the Athletics' depth.