"This year he has injured himself in three or four different places in the muscle area, I can't explain," said Haise.
France-born Boga picked up the injury ahead of last Thursday's trip to Brussels for a Europa League game against Union Saint-Gilloise which the French club lost 2-1.
According to his coach, Boga still needs additional tests to determine if surgery is required but club sources have estimated the 27-year-old forward will need at least three months to recover.
Boga is one of 10 Nice players who are absent for the team's Ligue 1 trip to struggling Montpellier.
Nice are sixth in the league table.
