-- His skills and speed have long been rusting, and now, the days when "Iron" Mike Tyson could wobble an opponent's knees with a fearsome glare are but a memory. That was proven beyond a doubt Friday night when unheralded British heavyweight Danny Williams stood up to Tyson and then scored a shocking fourth-round knockout of the former undisputed heavyweight champion at Freedom Hall.

"That intimidation factor," Williams said in a post-fight news conference, "is gone."

Tyson himself now may be gone, too -- from the ring, that is -- after a thoroughly disheartening loss to a 9-to-1 underdog. Tyson is 38, more than a decade-and-a-half removed from his prime and a shadow of the "Baddest Man on the Planet" who became the youngest heavyweight champion in history. He entered Friday's fight with a plan to recapture the heavyweight title and climb his way out of a $38 million debt. Now, his career, like his bank account, may be insolvent.

"It's definitely possible," said Freddie Roach, Tyson's trainer, when asked if his fighter would retire, "because I care about Mike. I don't want to see him get hurt."

He was hurt in more ways than one Friday. In addition to a cut near his right eye that required stitches and two brutal multi-punch combinations he absorbed, Tyson injured his left knee. After the fight, he was taken to Audubon Hospital for a CT scan and an examination of the knee. An MRI exam revealed a complex tear of the lateral meniscus, and Tyson couldn't walk on the leg Saturday, his manager, Shelly Finkel, told the Associated Press.

The members of Team Tyson who spoke Friday -- Tyson left the ring and then Freedom Hall without comment -- said they and Tyson did not want to use the knee, injured in Round 1, as an excuse. But they made it clear it hurt the fighter's mechanics and his ability to move and deliver punches with maximum power.

Tyson suffered the injury while throwing a left hook. He winced in pain, reached for the knee, then looked at the referee briefly before continuing to fight. He told Roach of the injury after the round.

"He told me that he couldn't turn left, he couldn't turn the hook over and was not getting much power," Roach said. "I told him he was going to have to suck it up and fight."

Tyson did, and appeared sharper than he had in years early in the bout. He was quicker and moved his head effectively to dodge and duck punches. He won the first three rounds on all three judges' scorecards.

The key for Williams was surviving an early, savage barrage of punches, including two left hooks in Round 1 that first staggered him and then left him clinging to Tyson to stay upright.

Williams hurt Tyson for the first time in Round 2 and continued to land punches from there. He still took some shots from Tyson, but Williams said the punches lacked the sting of their feared reputation.

Tyson has now lost two of his past three fights and is 5-4 in his past 11 (two were ruled no contests). But this defeat is the most difficult to digest. Not only was Williams not a champion or a former champ, such as Lennox Lewis or Evander Holyfield -- the other fighters Tyson lost to in his last 11 bouts -- he was an unknown lacking a marquee victory. Williams split his two bouts with Julius Francis, a man Tyson destroyed by technical knockout in the second round of their 2001 bout.

Tyson could ask for a rematch, as was discussed at the post-fight news conference. But does he even want one? Many at ringside thought Tyson could have beaten the referee's 10-count in Round 4 but chose to stay down. His chin never has been questioned. His heart, now, is a different story.

Roach said Tyson's financial problems, which he planned to solve by fighting six more times in the next three years, would not be a consideration when they discuss his future.

"Everybody needs to make money," Roach said. "Still, what Mike knows best is fighting. . . . But money won't be an issue whatsoever in our decision. What good is all the money in the world if you can't count it?"

Mike Tyson, more than $38 million in debt, sits on the ropes as Danny Williams waits after his knockout at 2:51 of the fourth round Friday night.