After a long rehab from offseason surgery, Boston Bruins defenseman Charlie McAvoy will make his season debut Thursday against the Calgary Flames.

McAvoy, the Bruins' top-pairing blueliner, underwent a complex left shoulder arthroscopic stabilization procedure on June 3 and was expected to miss at least six months. Boston coach Jim Montgomery, however, said Wednesday that McAvoy was ahead of schedule and "checking a lot of boxes" that would make him available for Thursday's game.

"I'm doing well," McAvoy said after Wednesday's practice. "We're just continuing to just stack these boxes up. Feel good about where we are and we're just going one day at a time. Getting excited [about coming back]."

Montgomery confirmed McAvoy will be back in his top spot with partner Matt Grzelcyk against the Flames, but didn't rule out some "mixing and matching" on the back end as needed. This is Montgomery's first season behind the Bruins' bench, but he's familiar with McAvoy's reputation as a game-changing defender.

McAvoy, 24, is coming off a breakout season offensively where he tallied 10 goals and 56 points in 78 games, including 21 points on the power play. He also paced the Bruins in ice time last year at nearly 25 minutes per game, although Montgomery doesn't see that heavy of a workload in McAvoy's immediate future.

"We're very fortunate with the D-corps we have, we don't need [McAvoy] to play 24 minutes," Montgomery said Thursday. "But I expect him to play 20 [against the Flames]. How he impacts the game in all three zones [is impressive]. It doesn't seem like he takes a second off. Whether he's pressuring pucks, he's ending plays, he's hitting someone or he's taking the puck from the breakout through the neutral zone, breaking the puck out and driving the net, we're getting a chance at the net."

The Bruins lead the Eastern Conference at 11-2-0, despite having missed both McAvoy and top winger Brad Marchand to start the season. Marchand had offseason hip surgery and returned for Boston on Oct. 27.