Dirk Nowitzki has never known anything like this offseason's "crazy" NBA free agency frenzy, which he believes is "good for the business."

NBA Finals MVP Kahwi Leonard is among the high-profile stars to have moved on, leaving the champion Raptors to join the Clippers.

Kevin Durant swapped the Warriors for the Nets, and Russell Westbrook and Chris Paul swapped places as the former left the Thunder to link up with the Rockets ahead of the 2019-20 season.

Jimmy Butler and Anthony Davis are among the other stars to have moved on to pastures new.

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Nowitzki, the retired Mavericks great from Germany, has found it hard to keep track of all the deals but says they will be great for the competition.

"It's definitely crazy. I was very surprised," said Nowitzki, who played in a charity soccer match in his homeland over the weekend.

"I've been in Europe for three weeks now and every day when I've switched on my phone there's been another announcement that someone had joined another team.

"I can't remember a time in my 20-year career when so many top players have changed teams. It was a crazy summer, but it's good for the business.

"There's been a lot of media coverage and it will be a crazy season. There's a lot going on."