Nowitzki is 14th all-time in the NBA in scoring with the most points in Mavericks history at 25,537. He scored more points for the club in every season since 2000-01 until his injury-plagued campaign last season paved the way for Mayo to lead the club with 1,255 in his only season with Dallas.
Nowitzki still led the team with 17.3 points per game.
The Mavericks (13-10) opted not to re-sign Mayo, who joined Milwaukee on July 13.
The Bucks (5-18), meanwhile, decided not to re-sign Ellis, who signed with Dallas on July 23. Ellis is averaging 21.4 points as the Mavs' top scorer, with Nowitzki at 21.1.
Since Mayo did not spend much time in Dallas, it's unclear what kind of reception he will get.
Ellis was booed repeatedly in his return to Milwaukee in the Mavs' 91-83 victory Nov. 9. He led four Dallas players in double figures with 18 points as his team built a lead as large as 19 points in the first half and held off a late rally.
Mayo led all scorers with 28 points to match a season high and said that the reunion with Dallas wasn't anything special.
"Nothing," Mayo said. "Just another game on the schedule."
While Dallas has enjoyed two days off before this contest, Milwaukee will arrive after a 91-90 home loss to Chicago on Friday. The Bucks are 1-7 in the second half of back-to-back contests.
The Mavericks also will likely have a key player ready to make his season debut. Brandan Wright is expected to play after being out with a small, non-displaced fracture to his left shoulder.
Wright has returned to practice and is eager to get back on the floor.
"Everything feels good, and I should be ready to go," Wright told the Mavericks' official website. "I should be ready to go, if all goes well. I'm not 100 percent sure, but I should be good."
Dallas will start a three-game homestand after a 2-2 trip ended with Wednesday's 95-93 loss to Golden State. The Mavs led by as many as 18 points before blowing a six-point advantage with 1:26 to go.
"Our guys fought hard," coach Rick Carlisle said. "It came down to a couple of plays. They made a couple, and we didn't."
Now Dallas will try to avoid its first three-game slide and improve to 5-0 at home against Eastern Conference foes.
The lowly Bucks are in search of three straight road wins as they try to recover from Friday's disappointment in which former Milwaukee forward Mike Dunleavy banked in a winning 3-pointer with 5.8 seconds left to beat them. They led by five with 90 seconds to go.
''It wasn't an easy shot," coach Larry Drew said. "It was a contested shot. But I'll say it again: It should not have come down it (that). We were in position where we should have closed that game out.''
Mayo scored 14 points after totaling 10 in his previous two contests.