ATLANTA -- If everything had gone right, right-hander Shae Simmons would have already made his long-anticipated return from Tommy John surgery. But after experiencing two setbacks caused by shoulder discomfort within the past month, the Braves reliever will remain sidelined without any clear indication of when he might be healthy enough to join Atlanta's bullpen.

Simmons was relieved when an MRI on Monday showed no structural damage to his shoulder. The Braves' medical staff diagnosed his ailment as latissimus dorsi tendinitis. Braves manager Brian Snitker said Simmons will spend the next couple of weeks resting and rehabbing at the club's Spring Training complex in Lake Buena Vista, Fla.

"It's got to be so hard on the kids," Snitker said in reference to pitchers returning from Tommy John surgery. "They work so hard and so long to get to that point, and then they have another setback. You've got to be really mentally strong to get through all of that."

Simmons was aiming for an early-June return when he made three consecutive scoreless appearances in the middle of May, before his Minor League rehab assignment was halted by some discomfort near his right triceps muscle. He returned to the mound on June 5 and made two more scoreless one-inning appearances before again experiencing similar discomfort.

While Simmons' surgically-repaired elbow has remained strong throughout the rehab process, he simply has not yet regained enough overall arm strength and durability to pitch on a regular basis.

Simmons posted a 1.35 ERA and limited opponents to a .162 batting average and .237 on-base percentage through the first 22 career appearances he made before his elbow began bothering him in July 2014. The 25-year-old reliever missed the final two months of that season and then felt more elbow discomfort that led him to undergo Tommy John surgery just before the start of Spring Training in 2015.

Odds and ends

• To fill the roster spot vacated by right-handed reliever Ryan Weber, who was optioned back to Triple-A Gwinnett after Monday's loss to the Reds, the Braves purchased the contract of left-hander Dario Alvarez from Gwinnett. Alvarez was claimed off waivers in May after he allowed 17 earned runs and issued 10 walks over 15 1/3 innings for the Mets' Triple-A affiliate. Since joining Gwinnett, Alvarez has allowed one earned run, recorded 14 strikeouts and issued four walks over eight innings.

• Braves shortstop Erick Aybar was scratched from Tuesday's lineup because of the lingering soreness he felt after getting hit by a pitch in the right ribcage by Blake Wood's 97-mph fastball during the sixth inning of Monday night's loss to the Reds.

Mark Bowman has covered the Braves for MLB.com since 2001.