To say that Dallas Mavericks owner Mark Cuban regrets letting Steve Nash walk away from the Mavs back in 2004 would be a complete understatement. So much so, that the billionaire still has one specific calendar note from nearly two decades ago that he's refused to remove since that fateful day.

Cuban recently opened up about how he continues to punish himself from what he considers to be the biggest regret he's ever had as a team owner:

“We made them what we thought was a great offer but Phoenix just came in and beat that offer,” Cuban said about the Mavs' initial offer for Nash, via Etan Thomas of BasketballNews.com. “I'll never forget it because he just called me up and he goes ‘They just offered me more than Mike Bibby'. You know Bibby just got a new contract and I have in town this calendar on my office still in the arena that I refuse to move and it's still there and it says ‘Nash = Mike Bibby money'. My biggest mistake ever. Nash hated me for a long time because of it.”

It is unclear how much the Mavs put on the table for Nash, who himself entered free agency in the summer of 2004. What we know is that he ended up signing a five-year deal with the Phoenix Suns worth $65.6 million.

For what it's worth, Mike Bibby was earning upwards of $10 million per season with the Sacramento Kings at that point in time, and clearly, the Suns believed that Nash deserved to be paid in the same range as the Kings point guard. Unfortunately for the Mavs, they were unable to match Phoenix's offer, and the rest, as they say, is history.

That's all water under the bridge now, but one thing that cannot be denied is how Mark Cuban still rues that decision to this very day. After all this is barely the first time the 62-year-old has admitted to that costly mistake.