The 27-year-old pitcher has not pitched in a Major League game since 2013 due to injuries. In addition to the elbow fractures, Parker has also had Tommy John surgery twice.
• Spring Training: Schedule | Tickets | Information
After learning of his injury, the A's gave Parker some time to consult with his family and doctors and were not expecting him to return to camp until Monday. However, the right-hander stopped by the clubhouse Sunday and spent some time on the bench during the game.
"He wanted to be here yesterday and we didn't think we'd have him here yesterday," A's manager Bob Melvin said Monday. "I know he feels good around the group of guys and he seemed to be in good spirits yesterday. The guys were happy to see him."
Parker's next step is still to be determined as both he and the club await the results of Tuesday's tests.
• All 162 regular-season A's games will be televised in 2016. CSN California will air 147 of the games, while ESPN and MLB Network will be showing the other 15.
• As the calendar inches toward Opening Day, rosters continue to shrink. The A's optioned a trio of players to Triple-A Nashville on Monday, including right-hander Andrew Triggs, whom the club claimed off waivers Thursday. Right-hander J.B. Wendelken and infielder Joey Wendle were also optioned.
William Boor is a reporter for MLB.com. Follow him on Twitter at @wboor. This story was not subject to the approval of Major League Baseball or its clubs.