Sale threw off the mound with Double-A Portland on Tuesday.
"So far, so good,'' Boston manager Alex Cora said before the Red Sox played at Tampa Bay. "He's in a good position. He feels great. I'll talk to him tomorrow and we'll keep moving forward.''
A seven-time All-Star, Sale was 103-62 with 2.89 ERA in his first nine major league seasons. He joined the Red Sox in 2017 and helped them to the World Series championship the next year.
But Sale had the worst year of his career in 2019, posting a 6-11 record with a 4.40 ERA, and then missed last season following March 2020 surgery to replace the ulnar collateral ligament in his left elbow.
The operation usually requires a minimum of 12 months of rehab but can take as much as two years. In his absence during the pandemic-shortened season last year, the Red Sox went 24-36 and finished last in the American League East. Entering Tuesday's game with Tampa Bay, the Red Sox held a half-game lead over the Rays in the division.