The Bobcats' key offseason acquisition was injured contesting Chris Bosh's shot in the third quarter of Charlotte's 86-75 loss to the Heat at the Sprint Center in Kansas City, Mo.
He limped into the Bradley Center on Saturday using crutches and wearing a walking boot. He'll wear the boot for several days before the ankle is re-evaluated. X-rays taken at the Sprint Center were negative.
"Obviously, it's not ideal, but it's part of being on a team," Bobcats coach Steve Clifford said. "It changes a little bit in terms of our master plan in terms of how we would implement offense, the order we would go. We'd been spending a lot of time obviously on the post-up aspect of it."
Jefferson had 11 points, seven rebounds and one steal in 23 minutes against the Heat.
The Bobcats start their season on the road Oct. 30 at Houston before returning to Charlotte Nov. 1 for the home opener against the Cleveland Cavaliers.
Jefferson has appeared in 628 career games with the Boston Celtics, Minnesota Timberwolves and the Utah Jazz.
Knee keeps Rose out of Bulls' win in Brazil
Derrick Rose missed the first NBA game played in South America on Saturday, sitting out the Chicago Bulls' 83-81 victory over the Washington Wizards with soreness in his surgically repaired left knee.
The NBA star's absence disappointed a sellout crowd of 13,635 at the HSBC Arena in Rio de Janeiro the gymnastics venue at the 2016 Olympics where the top ticket price for the preseason game was 2,000 Brazilian reals ($915).
Rose had played two preseason games without any sign of problems, but Bulls coach Tom Thibodeau said the knee flared up in practice Friday and Rose ended his work about halfway through the session.