Parker had sued the club for $20 mil ... claiming it should pay for the damage he sustained when he took a shard of glass to the eye in the bottle-throwing melee back in June.

In his lawsuit, Parker claimed W.i.P. should have been aware of the "bad blood" between the two stars ... and never should have let them inside the establishment on that fateful night.

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.