ARLINGTON -- Kendall Graveman's return to a big league mound will be delayed indefinitely.
The A's Opening Day starter, already subject of an early-season demotion, will have Tommy John surgery, manager Bob Melvin announced Tuesday.
Rangers team physical Dr. Keith Meister, who performed A's starter Jharel Cotton's Tommy John procedure in March, has been tasked with doing the same for Graveman. The right-hander will be sidelined for at least a year following the ulnar collateral ligament reconstruction.
"Unfortunately, that's where we've come with him," Melvin said. "It's too bad, because he got off to a little bit of a tough start, had to go down. It's a guy that's really invested in this team and really, in Spring Training and years past, he's been a leader.
"It's unfortunate he's having to go down this road right now. It's going to take him a little while to get back. So we're all feeling that a little today."

Graveman, 27, was winless in six starts with an 8.89 ERA and 41 hits allowed in 28 1/3 innings when he was optioned to Triple-A Nashville in April, returning to the A's for just one more outing on May 11 before he was sent back down again.
Graveman made two more starts for Nashville before hitting the disabled list with elbow issues.
"There were games where the velo was better than others, but he never said anything, and it wasn't really until the last one or two starts he had in Triple-A he started feeling anything," Melvin said. "Nothing popped up on the radar for us that would suggest that was altering his performance a little bit."
Chapman named Heart and Hustle Award winner
A's third baseman Matt Chapman has been named the A's winner of the Heart and Hustle Award, which is voted on by former players.
Selections are based on "passion, desire and work ethic demonstrated both on and off the field," per a release from the Major League Baseball Players Alumni Association.

"There's a lot of heart and hustle in what he does," Melvin said. "If anybody profiles for that award, it's him. There's a lot of dramatics, a lot of theater to his game, because he gets to so many balls that you wouldn't expect him to, and the way he plays the game, it's 100 percent all the time. There's no coasting, there's no going through the motions with him. He makes plays that nobody else makes, and on top of that he's a hard-nosed player. He deserves the award."
Worth Noting
• Infielder Franklin Barreto was optioned to Nashville to make room for Tuesday starter Frankie Montas. Barreto, whose fourth stint with the A's this year spanned 10 days, went 1-for-4 in two games.