Chris Sale will not be able to start the season because of a rib injury.
Sale has a stress fracture in his rib cage.
It will be weeks, not days, but no timetable was given for a possible return.
Sale had Tommy John surgery in 2020 and missed the entire season, but he came back strong last season.
He excelled after his return with a 6-1 record and 3.16 ERA in nine starts. The production for a shorthanded rotation helped the Red Sox reach the playoffs.
It showed the pitcher's upside when healthy, adding to a resume that includes seven All-Star selections from 2012-18 while finishing in the top six of Cy Young voting in each of those seasons.
Boston needs this production to stay competitive in the American League East, but the latest injury could be a problem if it forces him to miss time. The absence would put a lot of pressure on Nathan and the rest of the staff to pick up the slack.
Nick Pivetta, Rich Hill and Michael Wacha are projected to start in Boston.
The New York Yankees will play the Red Sox at Yankee Stadium on April 7.