Years ago, Mark Cuban allowed Steve Nash to walk -- after six successful seasons in Dallas -- and the Mavs star still hasn't forgiven himself, calling the blunder the billionaire's biggest basketball regret.
OSDB caught up with the 64-year-old owner in NYC this week ... and asked which move he kicks himself over in his almost 23 years of NBA ownership.
"Probably letting Steve Nash go. Yeah, I regret that. It's been almost 20 years now, and I still regret it," Cuban said.