Burnes (teres strain) suffers setback, likely out until Sept.

PHOENIX -- On his calendar, Torey Lovullo had three dates circled this year to mark the dates of the expected return of the Diamondbacks "Big Three" injured pitchers A.J. Puk, Corbin Burnes and Justin Martinez, who all had Tommy John surgery last year.

Wednesday, though, the Diamondbacks got bad news on Burnes.

The right-hander, who was expected to be back around the All-Star Break, suffered a strain of his right teres major muscle and now will likely be out until September.

"Those are big, big pieces for us," Lovullo said. "So it's a blow, and it's something that we're gonna have to deal with. It's just what we do in this game, and we've got very qualified players in that clubhouse, and they're gonna get some opportunities, and we've got five really good starting pitchers right now, and they're doing a good job. I want that to continue."

The good news for the Diamondbacks is that Puk is doing well in his rehab, tossing an inning in relief for Triple-A Reno on Tuesday night, and is expected back within a couple of weeks.

Martinez, too, is progressing, though the club does not expect him back until early-mid August.

The Diamondbacks signed Burnes to a six-year, $210 million deal prior to last season and he made 11 starts for them last year before injuring his elbow. The idea that he would be back midseason was something the organization hoped would be almost the equivalent of a Trade Deadline acquisition.

Burnes felt discomfort in his arm after he faced hitters for the first time in a live batting practice session last Friday and subsequent testing earlier this week showed the teres major strain. Burnes had thrown 15 bullpen sessions before facing hitters as part of his buildup and everything appeared to be on target with regards to his elbow.

While Burnes is one of baseball's better pitchers, which explains his large contract, the Diamondbacks rotation has pitched very well without him after struggling in late April.

Eduardo Rodriguez, Michael Soroka, Merrill Kelly, Ryne Nelson and Zac Gallen have picked up the slack for Burnes and they do have some added depth with Brandon Pfaadt, who opened the year in the rotation, now pitching out of the bullpen.

Lovullo said that Burnes would address the media in the very near future to detail exactly when he started feeling the discomfort and other details. Lovullo spoke with him at length recently.

"I was just trying to align with his frustration, just be present for him in my conversation," Lovullo said.

Burnes, who had only been on the injured list one other time in his career prior to last season, had been doing his best to remain patient with the rehab process, but was excited to finally face hitters after all the bullpen sessions.

"I'm sick of throwing bullpens," Burnes said on May 21. "Just getting better mechanically, getting cleaner, putting it in the right spot.

"I shocked, I think, a couple people today with the velocity, but it's been good. Now it's kind of the point now where we're making sure the shape of all the pitches are good."

Now, he'll have to be patient once again while the teres major heals and he can start the process of building up once again.