The 11-time All-Star underwent arthroscopic surgery on his right knee Oct. 19, an operation that typically requires a recovery period of three to six weeks before resuming basketball activities.
Nowitzki acknowledged that he expected to return at the lower end of that timetable and has been frustrated by the slow progress of his rehabilitation.
"I guess after every surgery you have some ups and downs," said Nowitzki, a 15-year veteran who had never undergone knee surgery. "You have some good days and you do a little more and you have a couple bad days.
"There were tons of bad days there a couple weeks ago. But it's getting better, and that's why we increased the workload starting yesterday."
Nowitzki, 34, has started running on an elliptical machine and pool treadmill, as well as riding an exercise bike, to get cardiovascular work. He has also started doing leg presses to try to build back strength around the knee.
The Mavericks, who have made the playoffs each of the last 12 seasons, are off to a 6-6 start without their lone superstar.
It has been difficult for Nowitzki to watch the Mavs, especially while they've lost five of their last seven games. However, he vows to resist the urge to rush his return, having learned a lesson when he struggled upon his return after a three-week absence due to a sprained knee two seasons ago.
"I'm not going to do that this year," said Nowitzki, who had never missed more than nine games in a season before this year. "I need to make sure everything's right before I come back. I can't rush. I'm hoping maybe after these two years to play a couple more years. So it would be the wrong thing now to push it and come back too early and maybe make something worse for the long term.
"So it's been learning to be patient the last couple weeks. It's not my favorite thing to do, but I just got to hang in there and stay positive and try to help the team wherever I can off the floor."