10:32 AM PT -- Duke fans can exhale at least a little bit ... Cooper Flagg just walked gingerly back onto the floor to join his teammates on the bench.

While it seems unlikely he returns to action Thursday -- it's obviously a positive sign that he's now moving around under his own power.

Look away, Blue Devils fans ... Cooper Flagg just hurt his ankle -- and based on how he needed a wheelchair to maneuver around after suffering the injury, Duke faithful should be holding its collective breath.

The 6-foot-9 18-year-old -- who many believe is a lock to be the No. 1 overall pick in the NBA draft later this year -- sustained the ailment in the first half of Duke's ACC Tournament quarterfinal matchup with Georgia Tech.

He went up for a rebound ... but when he came down, he badly rolled his ankle. He crumpled to the floor in pain -- and after needing assistance from teammates to get off the court, he was later seen being pushed around in a wheelchair.

So far, the team's given no update on his condition -- other than announcing he's doubtful to return to the tilt vs. the Yellow Jackets -- but if he were to miss any sort of extended time going forward, it could be catastrophic for Duke's title hopes.

The ACC Tournament will continue through this weekend ... and then the big NCAA dance will follow just days after -- speedy recovery, Coop!!!