GWS young gun Joe Fonti will miss the Giants' clash with North Melbourne after unsuccessfully contesting his rough conduct charge against Sydney superstar Isaac Heeney.

Fonti, who has played all six games this season, was given a one-match ban for a fourth-quarter incident involving Heeney in last Friday night's Sydney derby defeat.

The incident was graded as careless conduct, medium impact and high contact by match review officer Michael Christian.

GWS attempted to downgrade the impact from medium to low, as well as having the contact graded to body instead of the head.

But after deliberating for more than 40 minutes, the AFL tribunal upheld the charge, meaning Fonti will need to sit out this Sunday's clash with the Kangaroos in Canberra.

Fonti told the tribunal he was trying to smother the ball, but realised he wasn't going to be able to.

Instead of smothering, Fonti said he braced for contact with Heeney, arguing the impact was against Heeney's shoulder.

In the final case at the tribunal on Tuesday night, Gold Coast will try to overturn a one-game suspension for dashing defender John Noble.