Boston called up right-handed pitcher Ryan Brasier from the Triple-A Pawtucket Red Sox to replace Sale on the 25-man roster.
Sale made 27 starts in 2018, his fewest since 2014. He battled shoulder inflammation but avoided a more serious injury that often accompanies shoulder problems for pitchers.
The 30-year-old left-hander was his usual self on the mound when healthy. He finished with a 1.98 FIP and averaged 13.5 strikeouts per nine innings, per FanGraphs. His 6.2 WAR was fourth-highest among all pitchers despite the fact he threw only 158 innings.
Sale's 2019 performance has been a dominant storyline for the Red Sox for all of the wrong reasons. Through 25 starts, he's 6-11 with a 4.40 ERA and 3.40 FIP, uncharacteristically bad numbers relative to his past performance.
A year after winning the World Series, the 65-59 Red Sox are in a tough fight just to return to the postseason as the New York Yankees run away with the American League East.
Losing Sale for any amount of time won't help Boston's playoff odds.