Since finishing seventh at London 2012, Oates, based at Ratho, won Commonwealth Games gold in 2014 and earlier this year picked up silver at the European Championships, meaning he headed into his opening Olympic -66kg bout in confident form.
What’s more, he was facing Frenchman Kilian le Blouch, who he beat at the Jeju Grand Prix last year.
That time Oates won on golden score but in Rio the 33-year-old was on the wrong end of another nailbiter.
Oates was leading 2-1 with just seconds left only to pick up a debatable late penalty – shido – before again incurring the wrath of referee Annamaria Fridrich in extra time to hand victory to Le Blouch.
“It wasn’t good enough,” Oates said. “I left it down to the referee really in the end, the way the scoring and the shidos were going, instead of trying to open up a counter attack.
“I allowed the referee to dictate the fight and the decision at the end to give me a shido for not attacking was ridiculous.
“He is one of those fighters who doesn’t really want to get involved in a fight, he just wants to scrap you. I am usually good at a fight like that but I just didn’t really handle it here.
“We fought in Korea last year and it was almost an identical fight. It went to a golden score there and I won on shidos that time, this time it went against me.”
Oates will play no more part in Rio 2016 and admits that this defeat could also spell the end of his Olympic journey at the age of 33.
However, as the elder statesman of the Team GB judo team in Brazil, he knows he still has a job to do before he flies home.
“It is a long journey. Two years of qualifying, four years of competing, 28 years in the sport, I am 33 now so this is quite possibly my last Games unfortunately so it is disappointing,” he added.
“But we still have wonderful chances of a GB medal. ”
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