During this period, Tys on’s problems outside boxing were also starting to emerge. His marriage to Robin Givens was heading for divorce, and his future contract was being fought over by Don King and Bill Cayton. In late 1988, Tyson parted with manager Bill Cayton and fired longtime trainer Kevin Rooney, the man many credit for honing Tyson’s craft after the death of D’Amato. Following Rooney’s departure, Tyson began to stop using combinations to the body, relying less on the jab to work his way into the body, clinching more, using the Peek-a-Boo defense sporadically and throwing few combinations. In 1989, Tyson had only two fights amid personal turmoil. He faced the popular British boxer Frank Bruno in February in a fight where Bruno managed to stun Tyson at the end of the 1st round, although Tyson went on to knock out Bruno in the fifth round. Tyson then knocked out Carl “The Truth” Williams in one round in July.
In a fight on February 11, 1990, he lost the undisputed championship to Buster Douglas in Tokyo.Tyson was a huge betting favorite, but Douglas (priced at 42/1) was at an emotional peak after losing his mother to a stroke 23 days prior to the fight, and fought the fight of his life. Contrary to reports Tyson was in shape, despite lack of mental preparation sources note Tyson’s pronounced biceps and weight of 220 and 1/2 pounds, only 2 pounds more than he had weighed when he beat Michael Spinks 20 months earlier. Tyson failed to find a way past Douglas’s quick jab that had a 12-inch (30 cm) reach advantage over his own. Tyson did send Douglas to the floor in the eighth round, catching him with an uppercut, but Douglas recovered sufficiently to hand Tyson a heavy beating in the subsequent two rounds (after the fight, the Tyson camp would complain that the count was slow and that Douglas had taken longer than ten seconds to get to his feet).Just 35 seconds into the 10th round, Douglas unleashed a brutal combination of hooks that sent Tyson to the canvas for the first time in his career. He was counted out by referee Octavio Meyran.
The knockout victory by Douglas over Tyson, the previously undefeated “baddest man on the planet” and arguably the most feared boxer in professional boxing at that time, has been described as one of the most shocking upsets in modern sports history.