Jason Taumalolo has revealed that just two years ago North Queensland coach Paul Green gave him a stark warning - shape up or play your career in reserve grade.

Heading into Saturday's NRL grand final qualifier against the Sydney Roosters, the Cowboys international lock has firmly established himself as the game's most damaging forward.

The Kiwis Test frontman has this year run for more metres than any forward ever recorded after bulldozing 4707 metres, at an average of 196m a game, according to Fox Sports stats.

It's the second most metres by any player in a season since such records began - only behind fullback Roger Tuivasa-Sheck, who in 2015 ran for 5795m.

However, Taumalolo said that back in 2015 his career was at a crossroads after missing a team recovery session and was bluntly told by Green he risked slipping into obscurity.

"I definitely let the boys down," Taumalolo told AAP.

"Greeny said to me that if I was to play first grade, I definitely had to fix that or else he couldn't see me playing first grade.

"After that, I definitely turned that around. I've been professional and given everything a red-hot crack."

Two short years later, Taumalolo is a Dally M winner, premiership winner, and for two seasons in a row has led the league for most metres.

Taumalolo concedes discipline has been a problem during his career but has worked hard to turn change his ways.

The turnaround has been nothing short of stellar and earlier in the year he eschewed interest from the NFL and was signed to a 10-year deal worth a reported $10 million.

"A lot of Maccas and KFC," he says when asked what he's had to sacrifice to get where he is.

"I wouldn't say it was my weakness, but just being more professional.

"There was a time when I was always a turning up late to training or never on time for meetings. At times that cost me opportunities to play first grade.

"I spoke to some of the leadership boys back then and they told me if I was a chance to play first grade I needed to fix that.

"That's definitely a big factor in why I'm playing like I am."