Cuban said before Saturday night's game against Memphis that he wanted to be clear with Nowitzki that he was committed "through thick and thin" to getting the team back in contention.
Dallas recently fell 10 games under .500 for the first time since Nowitzki's second season in 1999-2000. Since then, the Mavericks have made the playoffs 12 straight years and won the title in 2011.
Nowitzki has a no-trade clause in his four-year, $80 million contract that expires after the 2013-14 season. The no-trade gives him the right to veto any trade, but he repeatedly has said that he intends to retire as a Maverick.
The Mavericks are playing with a revamped roster for the second straight season after Cuban decided not to bring back several key players from the championship team.
"I told Dirk we're not going to trade him. He was happy. I think," Cuban said, laughing. "I wanted to make it clear to him. I said, 'We're in this through thick and thin,' and so there's no way I would trade him, no matter what."
Nowitzki, who missed the first 27 games after the first knee surgery of his career, blew off some steam after a recent loss by saying the Mavericks couldn't count on landing a big name in free agency next summer after they missed on Deron Williams last offseason. It was an indirect shot at Cuban's decision to let Tyson Chandler and others go after the franchise's first title.
"When Dirk has something on this mind, he's never shy," Cuban said. "If he's going to tell you what he said in the media, you don't think he's going to dump on me? I mean, I've got texts from every single year and emails from every single year. Dirk wants to get it out of his system and then at the end of the email or text it's like, `Don't you worry. I'm a warrior and I'm going to lead these guys and we're going to get it rolling."
The Mavericks added guards O.J. Mayo and Darren Collison, center Chris Kaman and forward Elton Brand on short-term deals with the idea that they could pursue big names later, but also with the belief that the team could win now with Nowitzki. When the 7-foot German couldn't make it through training camp without pain in his right knee, Dallas was suddenly figuring out how to survive without him.
The Mavericks actually did OK at 12-15 while Nowitzki was out, but he was sluggish the first few games during a rough part of the schedule. Dallas lost nine of 10 and fell to 13-23 before beating Sacramento on Thursday in a game that also snapped an NBA record-tying 10-game overtime losing streak.
Nowitzki had a hand in a few of the defeats, missing key free throws late in losses to New Orleans and Miami.
"The odds of Dirk missing the free throws ... I would have taken that bet anytime, anywhere," Cuban said. "It just takes time. No one hurts more about it than Dirk. And there's nobody who's a bigger warrior and that's why I won't ever trade him."
That doesn't mean the Mavericks won't be active before the Feb. 21 trading deadline. Cuban said there was a "100 percent chance we're going to try to look to do something." He says the Mavericks could benefit from other teams trying to avoid harsher luxury tax rules that kick in next year.
Information from Tim McMahon of ESPNDallas.com was used in this report.