The Red Sox learned of Sale's positive test Thursday, according to the club. The left-hander was scheduled to start against the Chicago White Sox on Sunday.
"At this point, nothing shocks me, to be honest with you," Red Sox manager Alex Cora told reporters. "On a daily basis, we go through our process and we just hope for good news. This is where we're at.
"It's unfortunate, but he'll be back. He feels good. He actually feels great, and hopefully he can come back right away, right after his 'X' amount of days are done."
Due to the positive test result, Sale will have to sit out a minimum of 10 days under MLB protocols.
Sale becomes the 10th Red Sox player since Aug. 27 to test positive for COVID-19, with 11 others forced to sit out due to symptoms or close contact with positive cases.
The 32-year-old Sale, a seven-time All-Star selection, missed the entire 2020 season while recovering from Tommy John surgery. Since rejoining the Red Sox's rotation, he has posted a 3-0 record and 2.52 ERA in 25 innings over five starts.
Sale has a 112-73 record and 3.02 ERA across 317 appearances (237 starts) in his MLB career.