PITTSBURGH -- The Brewers placed Christian Yelich on the COVID-19 injured list on Tuesday after the star left fielder tested positive for a “breakthrough” case of the virus.

Yelich, who was fully vaccinated, began developing mild symptoms on Monday and alerted team officials, president of baseball operations David Stearns said. The Brewers’ charter flight to Pittsburgh was delayed from Monday evening to Tuesday morning while players and staff underwent testing and contact tracing.

As a result of that process, infielder Jace Peterson was also placed on the COVID IL because of contact-tracing protocols. Yelich must miss a minimum of 10 days, and his return is pending resolution of his symptoms. Peterson must miss at least seven days.

The Brewers and Pirates proceeded to play the opener of their three-game series as scheduled on Tuesday night.

“[Yelich] has taken precautions seriously and guidelines seriously through the season, and unfortunately yesterday he started developing some mild symptoms,” Stearns said. “He did the right thing and reported those mild symptoms. We got him a test yesterday afternoon and the test returned positive. We got him a confirmation test which also came back positive. …

“I talked to him this morning. He’s in good spirits. He’s resting, and certainly our hope is he can knock this out quickly and feel better quickly.”

All other players and staff tested negative for COVID-19, including Peterson, according to Stearns. Brewers manager Craig Counsell praised Yelich for reporting that he wasn’t feeling well, potentially preventing further spread of the virus, and wondered aloud whether the Brewers caught a break that Monday was an off day.

“We went through the MLB protocols last night and this morning. I’m very confident that we’ve satisfied those protocols,” Stearns said. “We’re doing everything we can to keep our group healthy and safe. As with everything in the world right now, we’re never going to be 100 percent sure. But I do think our group has taken this seriously from the beginning, and our medical staff has done a phenomenal job keeping everyone safe.”

"Breakthrough" cases of COVID-19, according to the Centers for Disease Control, are when a small percentage of people who are fully vaccinated still get the virus. Yelich and other Brewers players and coaches received the Johnson & Johnson single-shot vaccine in early April, and Yelich was among the players who participated in a public service announcement encouraging fans to get vaccinated.

The Brewers passed the 85 percent vaccination threshold in the first week of May, permitting relaxed protocols in the clubhouse, dugouts and other spaces.

At that time, right-hander Corbin Burnes was on the COVID IL and later revealed he’d had an asymptomatic case of the virus. Until Tuesday, Burnes had been the only Brewers player to appear on the COVID IL since the start of the pandemic.

“I think we all hoped we were past it,” Counsell said. “I think it's how we all want to feel, that we're past it or getting past it, but unfortunately we keep getting reminders that we're past the worst of it but it's going to keep popping up and we still have to deal with it.”

It’s been an intensely frustrating season for Yelich, who signed a club-record-setting contract extension just before the onset of the coronavirus pandemic in March 2020 after winning the National League MVP Award in ’18 and finishing runner-up in ’19. Since then, he has a .766 OPS in 125 games over the past two seasons, including a five-week stint on the injured list earlier this year with a low back strain. A quiet July (one home run, .628 OPS) has dropped Yelich’s slash line to .235/.382/.367 in 2021.

He was on a pace for 10 home runs and 45 RBIs this season as of Tuesday.

“I don’t think this has been his favorite year in totality,” Stearns said. “He’s dealt with a lot. And look, when I talked to him this morning, he wasn’t feeling great, but he was in good spirits. This was just another challenge that he’s going to overcome. He’ll get through this. He’ll be back with the team, and we’re going to certainly look forward to getting him back.”

While Yelich remained back in Milwaukee under quarantine, the rest of the Brewers landed in Pittsburgh at noon local time on Tuesday, seven hours before the first pitch of their series opener against the Pirates.

Yelich’s absence coincided with the return of outfielder Lorenzo Cain from the 10-day IL. Cain had been sidelined since suffering a right hamstring strain in a Memorial Day game against the Tigers. To replace Peterson, the Brewers recalled utility man Pablo Reyes from Triple-A Nashville.

“The absences aren't that long, so I think we should realize that we're fortunate there,” Counsell said. “Jace should be back by the homestand at the latest, we fully expect that. We're just going to have to fill in around them like we do with injuries. It's the same case and that's what will happen.”