Brazilian Alex picked up a thigh problem during PSG's 2-2 home draw against Barcelona in the Champions League quarter-final first leg on Tuesday but he is expected to be fit for next week's return leg at the Nou Camp.
"He's the only player who has had a problem. He can't play but he'll be back for Wednesday," Ancelotti told a news conference.
Motta has not played since late January because of various muscle strains.
"He's out again. I hope he will be available for Wednesday but there's still a doubt," Ancelotti said.
PSG have a seven-point lead over second-placed Olympique Marseille with eight games left but Ancelotti ruled out resting his key players ahead of the European clash at Barcelona.
"I won't make too many changes in my team. Tomorrow's game may be the turning point in the title race," he said.
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