Barry Sanders will tell story about his shocking retirement in new documentary

Ask football fans of a certain age to name their all-time favorite running back, and many will say Barry Sanders.

Ask them what they consider most shocking sports retirement, aside from Michael Jordan's first retirement, and the answer will also be Barry Sanders.

Sanders has spoke about why he stepped away from the Detroit Lions in bits and pieces since he retired right before training camp in 1999, but never in much depth. It's not a mystery that he was frustrated with the Lions and their perennial losing, but the whole issue has been left a bit unresolved.

But Sanders is ready to talk in a new Amazon Prime documentary, "Bye Bye Barry."

Barry Sanders documentary coming

The documentary is scheduled to be released Nov. 21, and the trailer will heighten the anticipation.

Like many recent sports documentaries, the main subject appears to be heavily involved with the making of the film. That usually leads to watered-down versions of events (having Urban Meyer be a key talking head in the wholly disappointing Netflix documentary on the 2000s Florida Gators meant we got more air time for LSU running back Jacob Hester than figures like Aaron Hernandez), but Sanders is promising that the "great mystery of why I walked away will be answered once and for all."

Fans couldn't believe Sanders would walk away, right after a 1,491-yard season and just 1,457 yards behind Walter Payton's all-time rushing record. Emmitt Smith would break that record instead.

Sanders was still great when he retired. Many couldn't figure out why he'd walk away just before setting one of the iconic NFL records. The way he retired was unusual. That all added to Sanders' legend.

Sanders departs the NFL abruptly

When Sanders retired, he sent a fax to The Wichita Eagle, his hometown paper. Nobody saw it coming. He didn't really explain in depth why he was retiring, just that "my desire to exit the game is greater than my desire to remain in it." After making that statement, Sanders went on a trip to London. He never had a retirement press conference.

Sanders has talked about retirement a bit since then. He wrote a book in 2003, and he discussed his dissatisfaction with the Lions.

"Management had let quality players slip away. We’d been losing for years," Sanders wrote in his book, via the Detroit Free Press. "Now we were right back where we were when I arrived.”

Other legendary athletes have retired out of the blue. Jim Brown did so from the movie set of "The Dirty Dozen." Andrew Luck's retirement leaked during an Indianapolis Colts preseason game with him on the sideline. Jordan stepped away after three straight NBA titles, leading to decades of conspiracy theories.

But Sanders' retirement was unique, given how beloved he was, how close he was to Payton's record and how little he said about it at the time and in the years that followed. Hopefully the documentary on his retirement is as enthralling as the subject matter.