Green, who is considered to be one of the top players in the NBA draft, will become the first known prospect to sign with an apparel company.
The 19-year-old averaged 17.9 points, 4.1 rebounds, 2.8 assists and 1.5 assists in 15 games to lead the Ignite in their inaugural season.
Green projects to have a bright future ahead given his dynamic ability on the court and potential to develop even further.
Vassell, who earned the start in place of Derrick White, missed his first four shots on Wednesday.
The Mavericks have won four of their last five games, and are coming off an impressive 133-103 blowout win on the road against the Warriors.