(WWLP) -The sports world is mourning the loss of Basketball legend Bill Russell who passed away on Sunday at the age of 88.

Bill Russell was the most prolific winner in American sports history. Russell is widely considered one of the greatest NBA players of all time. He led a Celtics team that rarely ever lost a title.

In addition to his 11 NBA Championships, 12 All-Star appearances, and five NBA MVP awards, Russell also won those last two championships as a player/coach in 1968 and ’69, a pair of NCAA titles with the San Francisco Dons in 1955 and ‘ 56, and an Olympic gold medal in 1956.

Russell is largely credited with writing the book on modern defense for centers. He perfected the art of blocking shots, swatting away would-be scorers with brutal efficiency without fouling and while keeping the ball in play so one of his teammates could gain possession. But he was much more than a basketball player.

Even as he brought Boston titles, Russell endured the era’s ugly racial resentment. He emerged as a leader in the American Civil Rights movement during the 1960’s, participating in the 1963 March on Washington with Dr. Martin Luther King Junior and supporting boxer Muhammad Ali after his decision not to participate in the Vietnam War.

Russell was honored with the Presidential Medal of Freedom in 2011.

President Obama said, “Bill Russell, the man is someone who stood up for the rights and dignity of all men. He endured insults and vandalism but he kept focusing on making the teammates who he loved better players and made possible the success of so many who would follow.”

Russell was enshrined in the Basketball Hall of Fame twice as both a player and a coach, a testament to his towering legacy as one of the sport’s all-time greats. He was one of a kind.