Team officials say Kelly will be monitored over the weekend and re-evaluated March 12.
The injury certainly will further test the focus of a team already trying to bounce back from a disheartening loss to North Carolina over the weekend that cost the Blue Devils the league's regular-season championship and the No. 1 seed in the tournament.
The pursuit of a fourth straight ACC tournament title for No. 6 Duke becomes much more challenging.
Kelly, a 6-foot-11 junior, averages 11.8 points and 5.4 rebounds while creating matchup problems because he is a scoring threat both on the perimeter and in the paint.
Second-seeded Duke (26-5) begins play Friday night in Atlanta against the Clemson-Virginia Tech winner.
''We've got a lot of incentive to go in there and win this one,'' guard Seth Curry said Tuesday, a few hours before Kelly's injury was made public.
''Hopefully, we'll win our first two games, and I hope we see Carolina again,'' Curry added. ''Go in there and try to win the championship. You want to put a banner up. That's your goal coming into the season, and we didn't do that in the regular season, so hopefully we can do that in the postseason.''
Five times since 2003, including last year, the Blue Devils (26-5) lost the regular-season finale to the rival Tar Heels and then went on to win the ACC tournament.
Mike Krzyzewski's Duke teams have won the tournament in 10 of the past 13 years, including three in a row, to give the school an ACC-record 19 titles.
No player on Duke's roster knows what it's like to lose a league tournament game; their last such loss came to Clemson in 2008, when the oldest player, senior Miles Plumlee, was still a senior in high school.
''Throughout the year, the main goal for a team is to land a spot in the NCAA tournament,'' Krzyzewski said. ''And then, if you have an opportunity as a result of pursuing that goal to win your regular season, then it's there. And we had that, and then we lost the game against North Carolina.
''So, it's easy to get on to the next thing, because that's not an ultimate goal,'' he added. ''The main goal is to make the tournament and be as high a seed as you possibly can, and then whatever happens as a result of pursuing, to me, that's a higher goal. ... But it's really very easy to get on to the next thing.''
Besides, the players say, there's no sense dwelling on one loss to the Tar Heels when — if the seeds hold — they'll meet again a few days later with another type of title on the line.
Curry says the feeling is ''real similar, honestly'' to last year when North Carolina won the season-ending matchup in Chapel Hill, only to lose to Duke in the tournament championship game.
North Carolina beat the Blue Devils in the 2009 finale before Duke took advantage of some bracket chaos — the Tar Heels were knocked out early after point guard Ty Lawson hurt his toe — to begin its run of consecutive league titles.
''I wouldn't say one's more important than the other, but ... you want to be peaking at the right time, going into the (NCAA) tournament,'' big man Mason Plumlee said. ''You want to go there and if you can win, get some momentum, get some confidence going into the (NCAA) tournament, it's a really good thing.''