Blue Devils spokesman Cory Walton confirmed to ESPN that Tatum, ranked second in the freshman class behind teammate Harry Giles, is being evaluated.
"We're not sure," Duke coach Mike Krzyzewski told SportsCenter on Wednesday morning. "It's not nearly the injury Harry has had. Still in the evaluation period. We'll find out more today and hopefully it's something minor."
Multiple sources told ESPN that Tatum suffered a foot injury and had to be helped off the court.
"He was terrific," one NBA executive told ESPN. "Right now, he's certainly in the mix for the No. 1 overall pick."
"He's so smooth and polished," said another.
Tatum was slated to start for Krzyzewski and the Blue Devils, who will likely go into the season without Giles, who is recovering from knee surgery. Giles missed his sophomore and senior seasons in high school due to knee injuries, but this last surgery -- performed just a few weeks ago -- is likely to keep him off the court for the beginning of the regular season.
Krzyzewski said Wednesday no structural damage was found in Giles' knee when surgery was performed Oct. 4.
Duke is the clear-cut preseason favorite to win the national championship this season, but without a healthy Giles and Tatum the gap would certainly be closed between the Blue Devils and teams such as Kansas, Kentucky and defending national champion Villanova.
Duke opens the season Nov. 11 against Marist.