21. Artis Gilmore
Artis Gilmore is what we like to call a “technicality.” He was actually a champion but it was in the ABA in 1975. He is also a 5-time ABA All-Star and a former MVP of that league in 1972. Gilmore landed on the All-ABA First Team 5 times as well as the ABA All-Defensive First Team too. He was clearly an insanely impressive player, so he was going to be an easy pick-up after the merger.
He did end up becoming a 6-time NBA All-Star during his time here but was never exactly the player he was in the ABA due to being 6 years into his pro-career by that point. However, he averaged around 18 points-per-game from 1976 to 1983, to start his career.
Though he averaged 15 rebounds a game in his ABA career, he was also impressive on the boards in the NBA too. For his first 10 years in the NBA, he averaged 10 rebounds a game. He even started out with 12 to 13 per game in the first few years. Artis was also a deadly assassin in the playoffs for both the ABA & NBA but sadly never got it done in the latter enough to get a ring.