Paris Saint-Germain star Neymar suffered a sprained ankle and a fractured metatarsal when he was stretchered off in Sunday's win over Marseille, the Ligue 1 leaders announced on Monday.
The Brazilian, who signed for PSG in a world-record move from Barcelona last year, is now a serious injury doubt for the Champions League last-16 second leg against Real Madrid at the Parc des Princes on March 6.
PSG trail in the tie after a 3-1 first-leg defeat in Spain, with their hopes of a maiden Champions League title taking a further serious blow with the confirmation of Neymar's injury.
"Additional examinations performed today (ultrasound and CT) confirmed an external sprain of the right ankle, but also an associated fissure of the fifth metatarsal," PSG said in a short statement.
Neymar is all but certain to miss Wednesday's French Cup quarter-final against Marseille and the weekend's Ligue 1 visit to Troyes, with the Real clash just three days later.
The club, who lead the French top flight by a massive 14 points, also said that centre-back Marquinhos had picked up a leg muscle injury.
The 26-year-old Neymar was stretchered off in anguish towards the end of PSG's 3-0 victory over their great rivals in the capital, having innocuously rolled his right ankle and flopped to the ground in pain.
With the game already as good as over, the stadium held its breath as he was treated and then carried away, with PSG forced to finish the match with 10 men having made all of their substitutions.
Neymar himself posted a picture on Instagram of his right leg with the ankle and foot heavily bandaged. "08:10. Finished for today," said the caption.
French newspaper Le Parisien had earlier reported that tests on Monday morning had ruled out a "fracture of a serious sprain".
But the club later confirmed their fans' worst fears, with the return game against reigning European champions Real just eight days away.
Despite the injury potentially benefiting Madrid, the Spanish side's coach Zinedine Zidane claimed he hoped Neymar would recover in time to play.
"I'm not happy with the Neymar injury and I hope he can be back for the game. I will never want a rival player to be out injured," Zidane said at a press conference in the Spanish capital earlier on Monday.
PSG have never reached the Champions League final, and lost at the last-16 stage last season after a humiliating 6-1 second-leg thrashing by a Neymar-inspired Barcelona, having won the first game 4-0.