Boston Red Sox pitcher Chris Sale began his rehab assignment Thursday in the Florida Complex League, finishing the day after throwing three innings in which he allowed zero runs on four hits and zero walks while striking out five batters.

Boston had planned for Sale to throw two innings, but the left-hander returned for a third inning of work.

The game was Sale's first since Aug. 13, 2019, when he was shut down with elbow inflammation but did not undergo Tommy John surgery. Sale tried to rehab the injury but eventually underwent the procedure in March 2020, missing the entire season.

Sale's return could bolster the Red Sox rotation heading into the playoff run. While All-Star Nathan Eovaldi has been excellent in 2021 -- posting a 3.66 ERA and 1.23 WHIP in 103 1/3 innings over 18 starts -- concerns about the rotation continue to grow. Garrett Richards and Eduardo Rodriguez have posted ERAs of 6.45 and 5.35, respectively, since the start of June, while Martin Perez and Nick Pivetta have 4.76 and 4.85 ERAs in the same time period.

Sale struggled during his last full season in 2019, tallying a career-worst 4.40 ERA and 1.09 WHIP in 25 starts.