Billy Slater played a key role in Queensland’s triumph over New South Wales in this year’s State of Origin decider.

It was a match that most players involved in will never forget, as more than 52,000 fans roared the Maroons to victory at Suncorp Stadium to seal the state’s 11th series win in 12 attempts.

But Slater can’t remember a second of it.

The full-back was badly concussed on Saturday following a crude hit from Canberra’s Sia Soliola, who was banned for five weeks, and in the aftermath it emerged that the Melbourne Storm star has lost two weeks of memory.

Watch the hit below

https://www.youtube.com/watch?v=I6lFR1GXdi0

As if we needed it, it was another reminder of how serious concussion can be, and Dr Corinna Van Den Heuvel, an expert in brain injury from the University of Adelaide, said the news is worrying.

“It is alarming. I’m sure for the player it is very alarming,” she told The New Daily.

“Post-traumatic amnesia [PTA] can be a consequence of concussion. It’s not common, though.

“And it is rare in concussion for PTA to extend for that period.”

Dr Van Den Heuvel said “it is possible” for Slater’s memory of that fortnight to return and that symptoms are “so different for everyone”.

She insisted that the way sports deal with concussion has improved, but that any athlete concussed “should not play or train for two weeks”.

Slater has already ruled himself out of Melbourne’s NRL clash with Manly this Sunday, but said he will play against the North Queensland Cowboys next weekend.

Former AFL player Leigh Adams – who retired in 2015 due to regular concussions – was diagnosed with clinical depression as a result of the many head knocks he received in his 104-game career.

The former North Melbourne midfielder was stunned to hear Slater had lost his memory for so long.

“I’ve never heard of someone losing it [memory] for that period so it is concerning,” he told The New Daily.

Slater celebrates Queensland’s Origin victory … which he can’t remember. Photo: Getty

“Every concussion I had – I never had it that bad. Sometimes I couldn’t remember the game, or maybe even most of that day.

“But the most would have been about five or six hours of memory loss. It’s not ideal.

“The good thing [for Billy] about playing sport at an elite level is the doctors and support you can get though.”

Adams said at its worst, his symptoms after a concussion – which included memory loss, anger issues and depression – could last up to 10 weeks and greatly affected his life.

“It was probably tougher on my family and my partner – I wasn’t aware I was lashing out,” he said.

The NFL example

In the same week Slater’s alarming revelation came to light, results of an American study into head knocks were published.

A neuropathologist examined the brains of 202 deceased American footballers, with 111 of them having played in the NFL.

Of that 111, a staggering 110 were found to have C.T.E (chronic traumatic encephalopathy), a degenerative disease suffered by those who have suffered repeated head knocks.

Adams said the findings were “very interesting” but was quick to highlight the differences between American football and Australian sports, particularly AFL.

“It seems pretty prevalent [over there]. I’ve seen a lot of specialists over the years, though, and they think it’s quite different,” he said.

“NFL players can be hitting heads 40 or 50 times a day, in training, and those symptoms are suffered more after continuous hitting of the head.”