Boston Red Sox manager John Farrell said Friday that closer Koji Uehara will go on the 15-day disabled list due to an injured left hamstring.
Retroactive to March 27, the right-hander will not be available to pitch until April 11 at the earliest, meaning he will not be part of the Opening Day roster.
"I'll just keep working day by day," Uehara, who turned 40 the same day, said in a statement.
Uehara missed a preseason appearance on March 17 after complaining of pain in his left hamstring.
Last season,he went 6-5 with 26 saves and a 2.52 ERA in 64 games.