Ex-NFL Star Hank Baskett Sued -- You Dirty (Gym) Rat

Hank Baskett -- the ex-NFL player who fumbled away the 2010 Super Bowl -- has his hands full with a new legal problem ... all over his involvement with a high-end L.A. gym ... TMZ has learned.

Baskett -- aka Kendra Wilkinson's husband -- is being sued by a couple of businessmen who invested in his "Performance Gaines" gym ... co-owned by Baskett's personal trainer Travelle Gaines (hence the name). The gym opened last fall.

The guys behind the lawsuit -- Jory Wolf and Nicholas Lorenz -- claim they dumped six figures into the project before Baskett's name was even attached to it ... and got left high and dry with nothing to show for it.

Wolf and Lorenz are pointing the finger primarily at Gaines, claiming Gaines tricked them into investing their money by promising a 40% share in the "Performance Gaines" business ... and then yanked the rug from underneath them, giving away their shares to other partners.

According to the lawsuit, Baskett was one of those partners ... so his hands are dirty too.

Wolf and Lorenz are suing for unspecified damages.