French Open crowd favorites Richard Gasquet and Gael Monfils are both questionable for the tournament with continuing injury problems.
Gasquet, who has not played since Miami, said his back injury improved after treatment but that he is lacking practice after a six-week layoff.
"I just began to serve again," he told Eurosport. "It was not easy. I just began to play points again as well."
The 27-year-old is expected to say whether he will play by Saturday, a day before the tournament begins.
Monfils has withdrawn from Nice with an ongoing ankle injury. "I moved around but not enough to play singles," he said.
Meanwhile, Janko Tipsarevic and Florian Mayer are reported to have withdrawn from the tournament.