Mark Cuban is sinking more than half a mil into a fantasy football trophies company called TrophySmack, and one of TMZ's former staffers is reaping the benefits!

Dax Holt was back with us for "TMZ Live" Monday to explain how he and his TrophySmack partner, Matt Walsh, managed to hook Cuban on the most recent episode of "Shark Tank.".

He tells us the trophy market was coming up short in terms of creative trophies to satisfy the smack-talking demands of modern-day fantasy football fans ...