The Upset: Buster melts Iron Mike

Mike Tyson returns to the ring Saturday (9 p.m. ET, Showtime PPV) when he meets Kevin McBride at the MCI Center in Washington. It's hard to believe it's been 20 years since Tyson made his pro debut. He turned pro on March 6, 1985, knocking out Hector Mercedes in the first round in Albany, N.Y., and it's been quite a ride since – inside and outside of the ring – as he became one of the most famous athletes on Earth. ESPN.com takes a look back at some of his most significant fights in this five-part retrospective.

Part III: The Upset
Quite simply, it is the biggest upset in sports history.

When James "Buster" Douglas knocked out Mike Tyson in the 10th round to become the undisputed heavyweight champion on Feb. 11, 1990, at the Tokyo Dome, he became the real-life Rocky, a 42-1 underdog who slayed Godzilla.

Tyson, at age 23, was the most feared fighter in the world, a knockout machine who didn't look like he could be stopped, and certainly not by Douglas, a decent-enough fighter with a record of 29-4-1 with 19 KOs. But Douglas' heart and work ethic were in serious question, especially after a 1987 bout against Tony Tucker.

They met for a vacant belt, and although Douglas was ahead of Tucker on the scorecards after nine rounds, he surrendered in the 10th. There was no way he would deal with Tyson's relentless onslaught, right?

Meanwhile, Tyson was 37-0 with 33 KOs and nine successful title defenses to his credit. He appeared well on his way to being hailed as the greatest heavyweight of all time.

But all was not well. Tyson had gone through messy splits with wife Robin Givens and manager Bill Cayton. He had split with longtime trainer Kevin Rooney in favor of less-experienced Aaron Snowell and Jay Bright. Tyson also was becoming increasingly difficult to handle and was slacking off in training. In a sign of what was to come, Tyson was knocked down by former heavyweight title holder Greg Page in sparring before the fight.

Still, Tyson was expected to blow through Douglas, like most opponents, including Tony Tubbs, whom he squashed in two rounds in 1988 on his first trip to Tokyo.

The Douglas fight was simply meant to be a vehicle to pocket an easy $6 million payday on the way to the really big cash. With Douglas an expected speed bump, Tyson already had signed to face Evander Holyfield that summer in Atlantic City.

What Tyson and the rest of the world didn't know was that this was not the same Douglas who had underachieved for so long and who had quit against Tucker.

This was a 29-year-old Douglas who was motivated and focused because of three serious personal struggles he was facing. First, Douglas was heartbroken over the death of his mother, who passed away less than a month before the fight. In addition, the mother of Douglas' 11-year-old son, Lamar, was seriously ill. Douglas had also recently separated from his wife.

Instead of allowing the problems to cloud his mind, he channeled that woe into the fight.

"Nothing compares to these last few months in the life of James Douglas," he told reporters in the days leading to the fight. "It [the problems] is a motivation, not a distraction."

Douglas looked good from the start of the fight, as he pushed Tyson back and took his best shots. However, Tyson was still giving it his all, round after round, despite badly swelling eyes, which his rookie corner was ill-equipped to handle.

In the eighth round, Tyson finally found the power and dropped Douglas. But Douglas was more mad than hurt, slapping the canvas because he was disgusted with himself for getting nailed.

Referee Octavio Meyran began counting and a clear-eyed Douglas paid close attention before calmly rising at nine, moments before the end of the round.

After the fight, Meyran's count would become the focal point of a major controversy. Tyson and promoter Don King asserted that Meyran's count was too long – at least 12 seconds – and that Tyson should have been declared the winner.

King even had the audacity to proclaim, "The first knockout obliterates the second knockout."

The WBC and WBA withheld recognition of Douglas as champion pending an "investigation." Only the IBF immediately recognized the new champion. The bogus argument was vilified around the world and eventually the sanctioning organizations relented a few days later.

The reason they did so came in the 10th round, when Douglas finally floored a fading, swollen Tyson with a brutal five-punch flurry.

The image is indelible: A badly disoriented Iron Mike Tyson on all fours, groping for his dislodged mouthpiece as Meyran counted him out at 1:23.

The mystique of the untouchable, invincible "Baddest Man on the Planet" had been shattered.

Dan Rafael is the boxing writer for ESPN.com.