A gut answer I had is Quinn Buckner, but I have no research to back it up. I believe he ended his career with the Celtics when they won a ring.
I do know he was the few to win a state (Illinois/Thornridge), NCAA (Indiana) and NBA championship in basketball. Maybe the only.
Quinn Buckner was my first guess as well.
Can't be Buckner, he started with the Bucks in 76 and they won their last Championship in 71-72.