"It certainly will move someone else in the middle," Blues general manager Doug Armstrong said. "Right now you can go with (Paul) Stastny, (Brayden) Schenn or have the option to go to (Vladimir) Sobotka back in there. (Ivan) Barbashev has played there, the young player we got from Pittsburgh - Oskar Sundqvist - he can play in there. There are some internal options and we'll explore those."
Armstrong also said he could evaluate free agency on July 1.
"We're always looking to see if we can get creative maybe," he said. "We're talking to some potential free agents, but I don't want to get anyone's hopes up that there will be a lot of change to this roster."
Berglund's surgery was performed by Blues Orthopedic Surgeons Dr. Rick Wright, Dr. Matt Matava and Dr. Matthew Smith at the Washington University Orthopedic Center.
Last season, Berglund posted a career high in goals (23) and finished with 34 points in 82 games played. For his career, the 29-year-old Vasteras, Sweden native has played in 637 regular-season games, scoring 151 goals and 145 assists (296 points).