Marlon Wayans -- Steve Nash is Too OLD AND BUSTED to Save the Lakers

Marlon Wayans pissed all over Lakers fans celebrating the Steve Nash pickup by declaring the former league MVP will be nothing more than an elderly cheerleader for the purple and gold.

Just a few hours after Nash -- aka 'Messiah 2.0' -- signed his deal with the Lakers, Wayans summed up the trade for the 38-year-old point guard by saying, "Steve Nash is a dead man. He's getting back massages at half court ... getting ice packs on."

But his ultimate diss was comparing Nash to "The Sixth Man" -- a god awful 90s movie Marlon made ... but NO ONE saw.