Allen, a 2011 fourth-round pick, is a first-year starter who is expected to replace Keenan Lewis, who signed with the New Orleans Saints in free agency. William Gay will likely take Allen's starting spot in his absence.
"We wanted him to get the surgery done now so he can begin rehabilitating immediately," coach Mike Tomlin said in a statement. "This surgery was a minor procedure and will have no long-term effects on his return to the field. We look forward to his rehabilitation process and having him back on the field in a couple of weeks."