The 40-year-old veteran has yet to take the floor after undergoing surgery in April to remove bone spurs from his left ankle.
He suffered a setback prior to training camp as a result of taking part in pickup games which made the tendon in his left foot flare up.
Mavericks head coach Rick Carlisle had Nowitzki listed as questionable for Wednesday's 114-107 victory over the Atlanta Hawks, but noted that he was "getting closer" to returning.
Robert Parish, Kevin Garnett, Kevin Willis, and Vince Carter all reached the 21-season mark, but played for multiple teams throughout their respective careers.
Nowitzki is a 13-time All-Star who guided Dallas to its only championship win in 2011 as the Finals Most Valuable Player. He currently sits as the Mavericks' all-time leader in games played, minutes played, points, free throws, 3-pointers, rebounds, and blocks.