The 21-year-old Slovenian star suffered a sprained left ankle in a painful game-three defeat on Friday that sees the Mavs trailing the Clippers 2-1 in the best-of-seven series in the NBA's quarantine bubble in Orlando, Florida.
On Saturday, Carlisle said it was too soon to say if Doncic would be able to play on Sunday afternoon.
"I believe that this is going to be most likely a game-time decision type of situation," Carlisle said.
"We're uncertain as to his status. We do not have the diagnostic test results yet, the MRI results, so that will certainly have something to do with it, and mostly it'll have to do with how he's feeling.
"I wish I knew right now, but I don't," Carlisle said.
"We have good depth to play without him, but he's one of the best players in the world, so if we have to play without him, it's a big loss."
Doncic insisted Friday night that the injury was "a little sprain" -- not nearly as serious as the two right ankle sprains that saw him miss a total of 12 games in December in February, before the NBA shut down in March amid the coronavirus pandemic.
Doncic was grateful that it wasn't his right ankle this time, and he even returned briefly to the contest after having the ankle heavily taped from twisting it in the third quarter.
He was clearly hampered, but did manage to record the first playoff triple-double in Mavs history with 13 points, 10 rebounds and 10 assists.
"I could run but I couldn't push off my left leg," said Doncic, who finally hobbled off for good after returning for some three minutes.
"He didn't further injure it," Carlisle said after the game. "He just wasn't able to move the way you've got to be able to move in a playoff game."