Tony Parker was at the nightclub the night Chris Brown and Drake's people got into that brawl. 

He lacerated his eye and was sent to the hospital and is suing the club for $20million. 

But now the nightclub is firing back, claiming Parker's got it all wrong ... because it's not the club's job to keep tabs on its patrons' personal lives -- so it can't be held responsible for not knowing about the beef.

Parker also claims the nightclub supplied booze to extremely intoxicated patrons, which helped fuel the brawl that led to the basketball player's injuries -- but the club says Parker's got no case ... so he can pound sand.

W.i.P. wants the lawsuit dismissed in its entirety. A judge has yet to rule.