WASHINGTON -- Giants manager Gabe Kapler said outfielder Mike Yastrzemski tested positive for COVID-19, leaving the club without a key left-handed bat for Sunday’s series finale against the Nationals at Nationals Park.

Yastrzemski represents the first coronavirus case of the year for the Giants, who were in the process of going through their post-contact protocol on Sunday morning.

Kapler said the Giants didn’t plan to add another player to the 28-man roster to replace Yastrzemski ahead of Sunday’s day game, though he expected a replacement to arrive on Monday, when they head to Milwaukee for the final game of their four-city, 11-game road trip.

Yastrzemski, 31, began to experience symptoms, including a sore throat, on Saturday, though he felt better after reporting to Nationals Park on Sunday, per Kapler. Still, the Giants felt it was prudent to get Yastrzemski tested, which confirmed the COVID-19 diagnosis.

According to Major League Baseball’s protocols, Yastrzemski will have to remain in Washington and isolate, though he can break the 10-day isolation period early if he returns two negative PCR tests. Yastrzemski entered Sunday batting .267 with a .696 OPS and one home run over 14 games this year.

“It really sucks,” Kapler said. “He was obviously playing really good baseball. He would have been in the lineup today, so it’s disappointing.”

The Giants reached the 85% vaccination threshold last year and placed only two players -- Donovan Solano and Alex Wood -- on the COVID-19 injured list in 2021. Several other teams, including the A’s, Mets and Red Sox, have already dealt with coronavirus outbreaks early this year.

It's unclear how much time Yastrzemski will miss, but as a reference point, Mets outfielders Brandon Nimmo and Mark Canha missed three and five games, respectively, after testing positive for COVID-19 earlier this month.