Paris Saint-Germain remained out in front at the top of Ligue 1, but Neymar 's injury put a dampener on a comeback victory over Saint-Etienne on Sunday.
The Brazilian went to ground in the closing stages of the 3-1 win, and was stretchered off the field of play before later being spotted leaving on crutches.
Lionel Messi set up all three goals for Mauricio Pochettino's side, with Marquinhos scoring twice and Angel Di Maria netting the go-ahead goal, as PSG took advantage of Timothee Kolodziejczak's red card to clinch victory.
However, they will have to cope without Neymar until 2022 after the extent of his ankle injury was confirmed, and his absence means the return of some of PSG's other injured stars couldn't come at a better time.
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"The examinations carried out last night confirm that Neymar Jr suffers from a sprained left ankle with ligament injuries," a statement from PSG confirmed on Monday.
The club revealed they expect him to be out of commission for the next six to eight weeks, though a further assessment will be made on Thursday to confirm the full extent of the problem.
If the initial estimates are accurate, Neymar can expect to miss at least four Ligue 1 games, as well as a Champions League match against Club Brugge, while he would remain a doubt for the first game back from the winter break on January 9.
It is the worst possible outcome for the French league leaders, who had initially hoped he would be able to resume action before the winter break.
There was some better news for PSG fans when it comes to some of their other players, with Marco Verratti returning to training today and Mauro Icardi expected to follow suit tomorrow.
Gini Wijnaldum and Ander Herrera are also both close to returning to training, having missed last week's Champions League defeat to Manchester City.
Julian Draxler is a bit further away, though, with a muscle injury expected to keep him out until mid-December at the earliest.
PSG moved 12 points clear at the top of Ligue 1 with Sunday's victory, while they are assured of a runner-up spot in their Champions League group regardless of their result against Club Brugge.
Neymar, who had a goal chalked off for offside at Saint-Etienne, was ruled out with ankle problems during the same period of the 2020-21 season and also suffered an ankle ligament rupture in 2019 which kept him out of that year's Copa America.
The 29-year-old will hope to be back in time to regain some match sharpness before his club resumes its European campaign, with a last-16 Champions League tie against one of the group winners coming up in February.
Injury kept him out of action for last season's last-16 tie against Barcelona, though he returned to play a part in the later rounds of the competition.