Nowitzki and his Holger Geschwindner told Nelson they would fly to Dallas and wanted to meet Thursday.
Nelson told The Associated Press it was a "really good sign" in the Mavericks' bid to re-sign its all-time leading scorer and rebounder, something Nelson said is crucial for the team's future.
"Everything else hinges on this," Nelson said. "We're going all-out. We'll get this thing done, and then we'll survey the rest of the field and figure out where to go from there."
He told reporters that there is no backup plan if the team doesn't bring Nowitzki back. Nelson said other big-name free agents and NBA stars won't be interested in coming to Dallas if there is no Nowitzki.
"There is no mix if there's no Dirk," he said.
Nowitzki is set to become a free agent at 11:01 p.m. Wednesday night after notifying the team he planned to opt out of the final year of his contract with the Mavericks.
Nelson had scheduled a flight to Germany to visit with the Mavs superstar and Geschwindner. By midday Wednesday, Geschwindner called the Mavericks and informed them he and Dirk planned to travel to Dallas on Thursday with plans to meet with Nelson at Dirk's Dallas home.
Mavs owner Mark Cuban will be in Los Angeles at the start of free agency, close to the agents for many of the biggest NBA stars, Nelson said. The bumper crop of free agents is headlined by LeBron James, but also includes Dwyane Wade, Chris Bosh, Amare Stoudemire and Paul Pierce.