SAN DIEGO -- The Brewers’ deep and talented starting rotation has sustained its first major hit, with All-Star right-hander Freddy Peralta facing a “significant” stint on the injured list after an MRI scan revealed the extent of his right shoulder injury.

The official diagnosis, per the team: posterior shoulder strain.

“He is going to miss a significant amount of time,” manager Craig Counsell said. “He will be back this season, but it’s going to be a lengthy absence. We’re confident that there’s going to be no aftereffects to this thing, but it’s going to take a while to heal and then build it back up.”

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Peralta exited his Sunday start against the Nationals complaining of tightness, and he and the Brewers hoped for the best. That was not to be, though the Brewers are hopeful at the moment that Peralta will recover in time to be a factor later in the regular season and lay enough of a foundation to start games in the postseason, should the team get that far.

The 25-year-old was the Brewers’ No. 3 starter to open this season and was 3-2 with a 4.42 ERA through his first eight starts. Last season, Peralta was 10-5 with a 2.81 ERA in 144 1/3 innings and made the National League All-Star team for the first time -- one of three Brewers starters and four Brewers pitchers on the squad.

His absence means an extended stint in the starting rotation for left-hander Aaron Ashby, who has been bouncing between the rotation and bullpen so far this season, his second in the Majors. Ashby was already scheduled to start the series finale Wednesday in San Diego before Peralta was injured.

“First of all, I hope Freddy’s all right,” Ashby said. “That guy is such a light in the clubhouse, and to see someone get hurt like that, it sucks for everyone. There’s definitely a spot to step up and help that team. Wherever I’m needed, I’m more than happy to do it.”

With Ashby graduating from sixth-starter status to a regular member of the rotation, the next man up, if needed, could be another young left-hander, Ethan Small, who is 3-1 with a 1.95 ERA this season for Triple-A Nashville. Small, ranked by MLB Pipeline as the top Brewers pitching prospect, missed his last start with a non-COVID illness but is penciled in to start Tuesday night at Toledo.

For now, Small will continue to develop in the Minors and the Brewers will proceed with five starting pitchers: Corbin Burnes, Brandon Woodruff, Eric Lauer, Adrian Houser and Ashby. Brewers starters entered Monday leading the Majors with a 28.2% strikeout rate and leading the NL in fWAR (4.3) while ranking second the NL in fielding independent pitching (3.34) and fifth in ERA (3.37).

“We have a very capable replacement in the starting rotation, but Aaron has impacted us in other places,” Counsell said. “The way we were trending, Aaron was probably going to impact us in the bullpen a little bit more as we move forward. So we lose that, and that means somebody else has to step up and try to set a very high bar with his performance here.”