The Red Sox are expected to be cautious with the left-hander's recovery from Tommy John surgery, sources told ESPN's Buster Olney.
Sale underwent surgery March 30. Players usually require 12-to-15 months to recover from the procedure.
While the Red Sox would love to have the 31-year-old contribute in 2021, they'd prefer to take a conservative approach, according to Olney.
Sale is entering the second season of a five-year, $145-million contract extension he signed with the Red Sox in 2019.
During his three seasons in Boston, Sale owns a 35-23 record with a 3.08 ERA and 13.2 K/9 in 84 starts.
Sale helped the Red Sox win the World Series in 2018.