Everyone knows about Papalii's big heart and the pictures of all the young kids in his locker that inspire the Canberra Raider every day of his NRL career.

Even the mullet he's sporting is raising money for a good cause.

And that same heart is the key to his amazing ankle tap of Gold Coast Titans halfback Jamal Fogarty on the weekend.

Papalii reached new heights in the speed stakes - clocked at 31.7 km/h or 8.8 metres-per-second - as he refused to let Fogarty race away for what seemed a certain try.

It's the fastest the powerful prop has ever run in an NRL game and was 3.4km/h - or 12 per cent - quicker than his previous best of 28.3km/h.

The man who trains Papalii and the Green Machine, head of physical performance Nigel Ashley-Jones, put it down to the competitive nature of the prop.

It was at a time in the second half when he could have easily given up the chase and let Fogarty cross for an 80m try from a quick tap at a 20m restart.

Fogarty had already burnt off Raiders hooker Tom Starling and prop Dunamis Lui, while England international John Bateman had also given up the chase.

Not Papalii though as his diving ankle tap brought Fogarty down and forced a turnover as well.

"He is the most competitive bloke in the world and he is the ultimate team man, and I think he found himself in a situation where he could make a difference and the opportunity has come," Ashley-Jones said.

"He ran about 31km/h. He's set his new speed record.

"He's very, very powerful and for a big man he's quick. He doesn't often run 30-40m at that pace so fair play to him.

"But Papa is as athletic as anything, he's very athletic. He's a big boy.

"It's what got him into his career was his athleticism. As we know now, he's not getting slower as he's getting older."

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Ashley-Jones said they hadn't done anything different with Papalii's training, except for the usual weekly speed training.

As far as speedsters at the club, he revealed Jordan Rapana, Bailey Simonsson (shoulder) and Jack Wighton were probably the top three - although Charnze Nicoll-Klokstad was also pretty slick.

The Raiders also have halfback George Williams leading the NRL for the fastest speed recorded in a game this season at 35.1km/h.

Ashley-Jones was hopeful Papalii wouldn't be called on to produce his try-saving chases regularly, but said the 112-kilogram prop - 35kg heavier than Fogarty - had raised the expectation levels.

"We'd rather he'd not do that in regards to our defensive system," he said.

"It was pretty phenomenal wasn't it ... We haven't done anything extra with him, but we cover all the bases anyway so that something like that can happen and they can handle it.

"They do a speed component every week. Papa's just a winner. It was phenomenal to watch."

Phar Lap's heart was one-and-a-half times heavier than a normal horse's and Papalii's is at least metaphorically in a similar mould.

He's joined a group of Raiders in growing his mullet throughout September to raise money for the Black Dog Institute.

John Bateman, Charnze Nicoll-Klokstad and Curtis Scott have also joined the cause.

NRL ROUND 16

Sunday: Canberra Raiders v Canterbury Bulldogs at Canberra Stadium, 6.30pm.