The world's most expensive player was missing from PSG's 2-1 loss at Olympique Lyonnais on Sunday and again for this tie due to what the club called "a pain in his right thigh".
Neymar was recently whistled by PSG supporters during an 8-0 thrashing of Dijon for denying Edinson Cavani the chance to score a club-record 157th goal from the penalty spot.
The 25-year-old hasn't been seen since, with claims of being injured preventing him from starting against Lyon and Guingamp in France's top flight and the Coupe de France respectively.
After a blazing start to his season at the French capital, Neymar's relationship with his teammates has deteriorated.
After controversial moves when leaving Santos and Barcelona, there's no reason to think the player will spend the rest of his career at Paris Saint Germain, especially with so much speculation going on lately.
Midfielder Sanson slotted in to complete the victory with just seconds left of injury time and secure the 10-time winners' progress into the next round.
Barcelona eventually swooped to scupper those plans, but Real have refused to give up on a long-standing target.
All of that has only added fuel to the fire that Real will try and lure Neymar to Santiago Bernabeu - and Neymar would even take a smaller pay package in a bid to convince Los Blancos to put plans in place to sign him.
"However, I hope that he will be available by February 3 [against Lille], at the latest".
It is something that needs to be handled in the dressing room - it is a shame.
The forward would have been allowed to leave last summer had Kylian Mbappe joined, but after he opted instead to move to PSG, Real president Florentino Perez is said to have promised Ronaldo a pay rise.
It is likely that according to multiple reports that Neymar will make a move to Real Madrid sooner or later.