The former Barcelona and Paris Saint-Germain star was absent from Monday's 1-1 league draw at Internacional as a safety precaution after expressing pain in his left knee in the clash with Mirassol on November 19th.
The 33-year-old has been constantly hampered by injuries across the year and has never really gotten started with his boyhood club, Santos.
Neymar had surgery on his left knee to reconstruct an ACL tear and a torn meniscus two years ago, and the club looks to have reoccurred once more.
Brazil boss Carlo Ancelotti, who is preparing his World Cup squad, expressed earlier this season that although Neymar has the quality, it is more about him being fit enough to feature next year.
"He is on the extensive list. He has six months to show his form. He needs continuity, minutes and physical condition, because talent alone is no longer enough in modern football.”
Santos play every three days, with travel and very little time for recovery, which does not help Neymar as he tries to return before the end of the season.
The Brazilian side currently sit 17th in the league standings and are close to being relegated. Neymar is very likely to be left out of the Brazil squad for the World Cup in what has been a nightmare year for the veteran who is coming to the end of his illustrious career.