Bret Thornton is making a habit of kicking bags of goals against rugby league converts, this time handing Israel Folau a football lesson on Saturday.

Thornton finished with six goals for VFL side Northern Bullants in their 89-point win over Greater Western Sydney in their Foxtel Cup knockout clash at the MCG.

Folau, the former NRL star who has signed to play for GWS in their debut AFL season next year, gathered two kicks and two handballs and looked totally clueless at times on Saturday.

His dropped marks led to goals for the opposition at least twice, his wayward kicking gifted Thornton a goal in the second quarter and his lack of tactical knowledge stood out like the smile on Andrew Demetriou's face after announcing the AFL's lucrative TV deal this week.

But as the 195cm Folau quickly admits, it's his first season learning the 18-a-side game and there are many challenges ahead.

Folau had one possession for the first quarter, a handball after earning a free-kick for a head-high tackle.

The key defender picked up two kicks in the second quarter and his effort in the eighth minute of the term summed up his day.

Under no pressure, the 22-year-old received a handball in the back pocket and drilled the ball 40 metres up the ground, straight into the arms of his direct opponent Thornton who kicked a goal on the run.

Thornton, a 164-game AFL veteran, kicked four of the Bullants' 12 first-half goals. They eventually won 19.9 (123) to 5.4 (34).

The 192cm Thornton's fifth goal came midway through the third quarter as Folau dropped a mark at full-back and two minutes later Thornton added his sixth, this time on a new opponent Josh Bruce.

Folau took zero marks on Saturday, while Thornton grabbed a game-high 10.

Thornton dined out for Carlton in round one of the AFL season at the Gabba, kicking four goals on another former Bronco Karmichael Hunt who was making his AFL debut.

Hunt has since shown some improvement for the Suns.

Folau failed to get a touch in a curtain-raiser against Sydney's reserves team earlier this month.

"I guess it's the running. It's something I need to get used to over the next year and hopefully I can improve," Folau told FoxSports on Saturday.

"Sheeds (coach Kevin Sheedy) has sent me back (into defence) to help to learn the game.

"I knew it was going to be a challenge. I'm just going to embrace it.

"(GWS assistant coach) Mark Williams is probably the man who has worked very closely with me. I have learned a lot off him."

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