Former Chicago Bears running back Gale Sayers has passed away after living with dementia. He was 77 years old.

The Hall of Famer is considered among the best running backs in the NFL, though knee injuries cut his career short. Sayers was inducted into the Pro Football Hall of Fame in 1977, after playing seven seasons with the Bears. He was 34 years old at the time, making him the youngest player voted into the Hall of Fame.

“All those who love the game of football mourn the loss of one of the greatest to ever play this game with the passing of Chicago Bears legend Gale Sayers,” Hall of Fame president and CEO David Baker said in a statement. “He was the very essence of a team player – quiet, unassuming and always ready to compliment a teammate for a key block. Gale was an extraordinary man who overcame a great deal of adversity during his NFL career and life.”

Sayers was born on May 30, 1943, in Wichita, Kansas and grew up in Omaha, Nebraska. During high school he was a football and track and field star, setting a state long jump record as a senior in 1961. He became an All-American at the University of Kansas and was a first round pick for the Bears in ’65.

Throughout his career, Sayers ran 4,956 yards and scored 39 touchdowns, mostly over the first five seasons of his career. Sayers was a five-time All-Pro running back who led the league twice in rushing, which included 1,032 yards in 1969 after he tore his ACL and MCL in his right knee during the previous season. As a returner, he scored six touchdowns and averaged over 30 yards per kickoff return and ran for two touchdowns and 14.5 yards per punt return. Sayers suffered an injury to his left knee in ’70 that led to his retirement in ’71.

After his football career, Sayers worked in athletics departments at two universities and founded a computer supply company. He wrote the autobiography, I Am Third, and his friendship with teammate Brian Piccolo was featured in the movie Brian’s Song.