The basketball world lost a real good one on Sunday after it was announced that Boston Celtics legend Bill Russell had peacefully passed away at the age of 88. The Hall of Fame big man was not exactly in stellar health, but it was a shock nonetheless to hear of his passing.

Tributes have come pouring in for the fallen NBA icon, and San Antonio Spurs head coach Gregg Popovich has come out with his own farewell message for Russell (h/t the Spurs on Twitter):

“Bill Russell’s legacy will live forever. He was a remarkable force, athlete, and human,” Popovich said. “His smile and approach were magnetic. His 11 NBA championships confirm he was the ultimate winner. Yet his most important achievements were the six decades he spent fighting tirelessly for civil rights and social change. He truly made the world a better place.”

While most tirbutes focused on Bill Russell’s achievements on the basketball court, coach Pop decided to turn his attention to what the 11-time NBA champion achieved outside the four corners of the court. In his mind, Popovich firmly believes that Russell’s tireless fight against social injustice is what sets him apart as a true icon of the sport. Russell had an undeniably significant impact on the sport of basketball, but coach Pop admires him even more for his activism.

Gregg Popovich is himself one of the most outspoken personalities in the NBA when it comes to social issues. He’s never shy to speak his mind, regardless if it’s the popular opinion or note. I’m certain that coach Pop looks up to Bill Russell in this respect.