Sydney Swans coach Paul Roos believes that gambling on pre-season NAB Cup matches should be banned in future so a repeat of the predicament he finds himself now in, won't happen again.

Roos and his club were sent a please explain letter from the AFL after an interchange steward informed the AFL he overheard Roos tell Jarrad McVeigh to "go forward, just don't kick a goal" in the closing stages of their two-point loss to Hawthorn in the opening round NAB Cup game last month.

Both Roos and McVeigh will head to Melbourne tomorrow to be interviewed by the AFL's investigator, former Victorian Court of Appeals judge John Winneke.

Roos faces a maximum $100,000 fine and indefinite suspension over claims he instructed a player to miss a goal in the pre-season competition.

AFL chief executive Andrew Demetriou has backed the investigation, saying it is no lesser an offence to throw a game in a pre-season match or regular season match because punters still place bets.

Roos today countered the argument, suggesting betting should be banned on NAB Cup matches.

"You're not going to have a charge on a NAB Cup game based on gambling if there's no gambling on NAB Cup games," Roos said.

The Swans coach, who has never won a pre-season cup game in his six seasons coaching at the club, said he did feel as though there had been a slight on his character when the term match-fixing had been used in reference to the matter.

"If you link it back to match fixing, it can be a bit of a slight on your character," Roos said.

"I know what I represent as a person, I know what I represent for this footy club and for his group of players and as long as you are comfortable when you put your head down on the pillow at night and you can go to sleep that's the main thing.

"I think if you link this into gambling, which this charge is obviously linked into, then yeah I guess the answer is quite simply yes (to ban gambling on pre-season games), because you're not going to have a charge on a NAB Cup game based on gambling if there's no gambling on NAB Cup games."

Asked how disappointed he would be if he was sanctioned or fined by the AFL over this incident, Roos replied: "I'll tell you if and when it happens."

Roos said he has never sent a player out with instruction not to try.

"In terms of players trying, they tried really really hard against Hawthorn and we came up short."

With AAP