Alvarez is scheduled for five to six innings with Nashville, and if he can get up to around 70 pitches, the A's anticipate releasing him from what's been a lengthy rehab.
It will be his second rehab start since suffering a May setback, and the A's can't afford another, given their dire situation with a beleaguered rotation that entered the day with a 4.72 ERA, including a 6.35 ERA dating back to April 23.
"It's worrisome to see your teammates going down and not being able to do anything," Alvarez said through a translator.
An All-Star in 2014, Alvarez owns a 3.80 career ERA. He last pitched in a Major League game on May 22, 2015, for the Marlins, and signed with the A's as a free agent last offseason.
"We were looking forward to his starts in Spring Training, let alone right now," Melvin said. "Well documented we've had some issues with some injuries and some performances that have taxed our bullpen some, so we're very much looking forward to getting him back."
The A's have yet to name a starter for Saturday's game against the Angels, though right-hander Zach Neal remains in play, despite pitching in relief Monday and Tuesday. Left-hander Eric Surkamp is listed as Sunday's starter.
• Right fielder Josh Reddick (fractured left thumb) hit soft toss Wednesday and is slated to take batting practice Friday, as he continues to progress ahead of schedule. Reddick could begin a Minor League rehab assignment as soon as next week.
• Melvin gave outfielder Coco Crisp his second consecutive day off Wednesday, allowing him to rest a sore Achilles, but he expects the veteran to return to the starting lineup for Thursday's series finale against Texas.
• A's third-round Draft pick Sean Murphy, a catcher out of Wright State University, has signed for $753,100.
Jane Lee has covered the A's for MLB.com since 2010. This story was not subject to the approval of Major League Baseball or its clubs.