The source said doctors expect the procedure on Roethlisberger's knee to be a "cleanup," not a full repair of the meniscus, and this generally favors a quicker recovery.
The Steelers won't know how long Roethlisberger will be sidelined until after the surgery, but he will definitely miss at least next Sunday's game against the New England Patriots, according to the source.
Speaking on WEEI's Kirk and Callahan Show on Monday, Patriots quarterback Tom Brady said he expects Roethlisberger back on the field sooner than later.
"He's one of the toughest guys in the league. I would never rule him out for anything," Brady said. "... He's done that before and played and thrown for 400 yards. He's just a stud, just an incredible player. I've played against him since 2004, and nothing surprises me with him. He's one of the best quarterbacks I've ever played against. I would never count him out."
Roethlisberger's injury was first reported by the Pittsburgh Post-Gazette and confirmed by ESPN.
Roethlisberger was sidelined with 8:18 left in the first half of Pittsburgh's 30-15 loss to the Miami Dolphins on Sunday. He was running a bootleg away from Dolphins defensive end Mario Williams, who appeared to nick Roethlisberger's leg as the quarterback made his way out of the pocket.
Roethlisberger said after the game that he "felt something funny in my knee," which prompted a trip to the locker room.
Upon a first evaluation, the team doctor thought Roethlisberger's leg had hyperextended from the contact, said Roethlisberger, who also has bruising in his right knee from a separate, late-game collision.
Backup Landry Jones played one full series in place of Roethlisberger, who finished 19-of-34 for 189 yards, one touchdown and two interceptions. Roethlisberger played the entire second half.
ESPN's Jeremy Fowler and Mike Reiss contributed to this report.
Roethlisberger tears meniscus against Dolphins
Steelers quarterback Ben Roethlisberger sustains a torn meniscus in his left knee during the second quarter against the Dolphins while being chased by Mario Williams. Roethlisberger went to the locker room but returned to the game.