Red Sox manager John Farrell said Monday that Miller has damage to the ligament in the foot, which he hurt while backing up a play at home plate Saturday against the Angels. Miller flew back to Boston on Sunday and was examined Monday by the team's foot specialist, Dr. George Theodore.
"He's going to need surgery and it's unlikely he'll be back this year," Farrell said at Safeco Field. "There is damage to a ligament that has to be repaired."
An MRI revealed the damage. No date for the surgery had been scheduled.
"Given the way he has pitched and that he is a power left-hander in the bullpen it is [a significant loss]," Farrell said.
Miller, in his second full season as a reliever for the Red Sox, had a 2.64 ERA while striking out 48 in 30 2/3 innings.
He showed improved control after the Red Sox worked with him to reduce his big leg kick this offseason.
"There's many examples of lefties coming along at different points and times in their career, and he was an example of that," Farrell said. "It was happening a little bit later in his career than we first anticipated. He was well on his way to becoming a dominant left-handed reliever."
Information from ESPNBoston.com contributor Adam Lewis and The Associated Press was used in this report.