Mark Cuban Says His Biggest Regret Is Letting Steve Nash Leave Mavs

Years ago, Mark Cuban allowed Steve Nash to walk -- after six successful seasons in Dallas -- and the Mavs owner 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.

Of course, Nash played six seasons in Dallas, and even made two All-Star teams. But, when his contract expired in 2--4, Steve left for the Phoenix Suns.

At the time, Nash said he was "sad to leave my teammates," but excited to be "going somewhere where they really wanted me."

He went on to win back-to-back NBA MVP awards.

It's not that things didn't work out for the Mavs, too. They made the Finals in 2006, losing to the Dwyane Wade and Shaquille O'Neal-led Miami Heat.

Then, in 2011, the Mavs once again made the Finals ... but this time, Dirk Nowitzki wouldn't be stopped. Dallas beat LeBron James' Miami squad in 6.