DALLAS -- The Dallas Mavericks signed forward Dirk Nowitzki to a contract extension Tuesday that's believed to be worth about $90 million over six years.

"This is a very special day for me," Nowitzki said in a statement released just after the Mavericks and Orlando Magic tipped off their preseason game Tuesday night. "We have a great organization and great fans. I am very happy that I will continue to play in Dallas."

The deal, which kicks in after this season, had been close to being finished for so long that the team put in its media guide that it was completed Oct. 1. The primary holdup was a medical problem that prevented Nowitzki's agent from traveling to Dallas from Germany.

The team cited policy in not releasing contract terms.

Nowitzki is coming off a breakout season in which he led the Mavericks in scoring (21.8 points per game) and rebounding (9.2 per game), while helping them win 53 games and reach the second round of the playoffs. It was Dallas' best season in 12 years.

Nowitzki showed his toughness by playing through a lost tooth in one playoff game and displayed his ability to take over a game by scoring 42 points and grabbing 18 rebounds in another. He led the team in scoring and rebounding again in the postseason.

The 7-foot, 245-pound forward is versatile enough to play anywhere from small forward to center. He, Michael Finley and Steve Nash are billed as the team's Big Three because so much of the Mavericks' success hinges on them.

"Dirk started his NBA career as an unknown," said coach-general manager Don Nelson. "In the last three seasons, he has developed into one of the finest players in the NBA. This is a proud day for me and the Dallas Mavericks organization."