A quirk of the tribunal system meant Brisbane's Black, the 2002 Brownlow Medallist, remained eligible for the award despite pleading guilty to reckless umpire contact.

Port Adelaide tried to have Thomas' charge downgraded from reckless to negligent because he had a 20 per cent loading for a previous offence.

After a lengthy hearing, Port's bid failed and Thomas became the first player to be suspended under the league's push this season to stop players colliding with umpires at stoppages.

Like Sydney co-captain Brett Kirk a fortnight ago, Black and Thomas effectively rolled the dice by setting up behind the umpire at a bounce.

The AFL wants to keep players out of the unofficial ''no-go'' zone behind a field umpire for when he backs away from the bounce or ball-up at a stoppage. ''We thought it was very, very similar to the Kirk one ... with Matty's 20 per cent loading, it was going to cost him a week,'' said Port football manager Peter Rohde.

''So we were keen and I know a few of the other clubs were encouraging us to test the rating the match review panel had given it.

''It wasn't disputed in there I don't think that Matt tried to avoid the contact, but once he set up in that position, it made it very hard for him to get off [the charge].

''Certainly if there's any contact when you set up in that position, it's going to be pretty extenuating circumstances, I'd reckon, to be able to prove you're not guilty.''

The one-match ban means Thomas will miss Friday night's home match against unbeaten St Kilda.

Under the tribunal system, Kirk, Thomas and Black could not take early pleas for the reckless umpire contact charge with the match review panel recommending the same penalty for all three 125 demerit points and a $2600 fine. AAP