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Tyson's pro debut was witnessed by just 2,000 fans in Albany, New York. Bizarrely, his own trainer - Kevin Rooney - was fighting in the card's official main event.
But the roar that goes up when the teenage heavyweight is introduced makes it obvious who the small crowd are there to see. Tyson did not disappoint as he battered his opponent.
March 6, 1985: An 18-year-old Mike Tyson makes his pro debut.- DAZN Boxing (@DAZNBoxing) March 6, 2021
The rest is history :clapper:pic.twitter.com/vFT6Vr8eNN
"The night of the fight, I was nervous," he admits in his autobiography, Undisputed Truth. "But I knew I could beat the guy as soon as I saw him in the ring."
Puerto Rican Mercedes was 19 years young himself and 0-3 in his three pro fights. Number four lasted just one minute 47 seconds, but was probably the most painful yet.
Sporting his stripped-back, no frills in his look - but in white rather than his iconic black - Tyson started the aggressor before Mercedes actually landed a pair of left hands, to no notable effect.
A glancing right hand soon sent Hector staggering backwards, at which point Tyson decided to crash test the chassis of this particular Mercedes. Eye-watering hooks from either fist torqued into Hector's flanks before he wisely sat down in the corner.
He rose at around the 10 count, but with the body language of a man wondering why his ribs were now inside his lungs rather than ready to go back to war. The referee waved it off, as the crowd booed, the bloodthirsty swines.
Remarkably, given the multimillion-dollar paydays he'd make, Tyson's pro debut failed to sell out and actually lost money. His manager Jimmy Jacobs shelled out the boxer's modest $450 earnings.
"I hardly made any money from those early fights," Tyson said. "My first fight lost money for the promoter, but Jimmy gave me $500. Then he took $50 from that to give to Kevin and he put $350 in the bank for me, so I walked away with $100."
These early fights served their purpose, however. Tyson's frustrating failure to qualify for the 1986 Olympics meant there wasn't a huge buzz when he turned professional - meaning his management had to build hype around him in an innovative way.
So they incessantly mailed videos of Tyson's early, brutal KOs to boxing journalists across the USA. Mike kept adding to his highlight reel, winning a remarkable 18 fights - all by knockout - in his first 12 months as a pro.
Soon the teenager with the tank physique, who drilled holes in his opponents with his eyes before he did the same with his fists, was the most talked about prospect in boxing.
However back in 1985, his mentor Cus D'Amato was there to keep his feet grounded.
"I was excited," Tyson recalled after his first victory, "but back in the dressing room, Cus pointed out all my flaws. 'You gotta keep your hands up more. You were playing around,' he said."
D'Amato passed away in November 1985, so wasn't present to witness it - but in 1986, Tyson violently tipped over Trevor Berbick to become the youngest world heavyweight champ ever.
The nervous kid who couldn't fill out a 3,000-seater venue on his debut had, 18 months later, become the baddest man - and biggest draw - on the planet.
Image credit: PA Images
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