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Anonymous/Associated Press

For decades, Gale Sayers has been the poster boy for a promising career cut short by injury.

As a rookie in 1965, he finished second in the NFL in rushing and won Rookie of the Year. In his second season, he won the rushing title, picking up more than 1,200 yards on the ground and averaging 5.4 yards per carry.

On a per-touch basis, Sayers was having an even better year in 1968, averaging a gaudy 6.2 yards per carry. But one week after he tallied a career-high 205 rushing yards against the rival Packers, Sayers tore his ACL, MCL and meniscus in his right knee during a game against the 49ers.

When Sayers returned to the field in 1969, it was clear that he had lost a step. But he still led the league in rushing and was the only 1,000-yard rusher that season.

During the 1970 preseason, Sayers suffered an injury to his other knee. The then-27-year-old tried to play through it, but he ultimately had surgery and was ruled out for the remainder of the season.

He would play two more games and gain 38 yards on 13 carries before announcing his retirement in 1971.

That Sayers was a no-brainer inductee into the Hall of Fame is a testament to just how great he was when healthy. Former teammate Johnny Morris said Sayers was as dangerous a runner as any man who ever played, according to Mark Potash of the Chicago Sun-Times.

"I played with Gale. I covered Payton [as a sportscaster/announcer], and I've covered a lot of guys over the years. If I wanted one player for a season, I'd take Walter Payton. But if I wanted a player for one play, I'll take Gale Sayers—above every running back I've seen, whether it be Jimmy Brown or O.J. Simpson."

It's fascinating to wonder what Sayers might have been capable of in the modern era.