Ultimately, Barry Sanders' reasoning behind his shocking retirement was as simple as the fax he sent the Detroit Lions to inform them of his plans to hang up his cleats. 

Sanders, who stunned everyone when he retired just as the Lions were going into training camp in the summer of 1999, recently opened up on his decision to walk away while still in the prime of his career. 

"For me, just that thing that drove me to play, which is that passion, just wasn't there," Sanders said in Amazon's new documentary on the Hall of Fame running back. "There was nothing really left to play for. I didn't see us as any kind of a serious Super Bowl contender. ... I felt like I was making a pretty clear decision. I just felt like, in my mind, this is pretty much it." 

Sanders' comments on the matter in 2023 are similar to the ones he penned in the article announcing his retirement 24 years earlier. 

"The reason I am retiring is simple: My desire to exit the game is greater than my desire to remain in it," Sanders wrote. "I have searched my heart through and through and feel comfortable with this decision."

As discussed in the documentary, there were factors that ultimately led to Sanders no longer having the drive to continue playing. The main reason was that the Lions were 5-11 in Sanders' last season and appeared to be light years away from being a legitimate contender. The fact that the team had parted with several of the team's core players during Detroit's more successful years during Sanders' tenure didn't help matters. 

The Lions made it to within a game of the Super Bowl during Sanders' third season but did not win a playoff game in any of his final seven seasons. While Sanders stayed, he watched as several of the team's better players during those years left town. Pro Bowl center Kevin Glover's departure after the 1997 season, for example, had a profound impact on Sanders, who would retire the following offseason. 

"You go to war and go to battle with those guys, you form a bond, obviously," Sanders said. "Some of the guys that they may have brought in to replace those guys were just not the same, but you've got to take the field with the guys you practice with. ... Had that group been able to stay together, somehow, we definitely could have done much better and definitely would have won some playoff games." 

Sanders retired despite being just 1,458 yards away from breaking Walter Payton's iconic career rushing record. He likely would have broken Payton's record that season as he had just rushed for 1,491 yards in 1998 in what considered a "down" year for him. Sanders had rushed for at least 1,500 yards each of the previous four seasons and rumbled for 2,053 yards during his 1997 MVP season. 

Emmitt Smith eventually broke Payton's record in 2002. But had Sanders had decided to keep playing, many feel -- Smith included -- that he would have become the first running back to rush for 20,000 yards. 

While he didn't break Payton's record, Sanders' legacy is secure. He is considered one of the greatest players in NFL history and is in any conversation regarding the top running backs in league annals, a select group that also includes Payton and Jim Brown, the NFL's career rushing leader until Payton passed him in 1984. 

Sanders' legacy as an all-time great was cemented in 2004, when he became the second-youngest player to ever be inducted into the Pro Football Hall of Fame. 

Numbers aside, Sanders' true greatness was his uniqueness as a runner. Arguably the most elusive running back ever, Sanders' vision, cutback ability and cat-like reflexes were second to none. He routinely made jaw-dropping runs that had never seen before and haven't been seen since.