Mark Cuban is so hands-on as the owner of the Dallas Mavericks -- he even attends ALL of his teams' G-League games ... so says Kostas Antetokounmpo.
Kostas -- a 2nd round pick in the 2018 NBA Draft -- is the younger brother of "Greek Freak" Giannis Antetokounmpo ... and currently plays for the Mavs' developmental team, the Texas Legends.
The 21-year-old is averaging nearly 10 points and 6 rebounds per game and has a ton of potential -- but when we saw him at LAX, he told us how great it's been playing for Cuban.