Port Adelaide are preparing to appeal Zak Butters' fine for umpire abuse, believing the star midfielder has been branded a liar by the AFL tribunal verdict.

As the AFL Players' Association expresses deep concern at the tribunal not believing Butters' testimony, Port chairman David Koch is "pretty certain" the club will appeal.

"Zak is a competitor but he's one of the nicest blokes you could ever meet," Koch told Adelaide radio station 5AA on Wednesday.

"He's incredibly angry with the outcome. He quite rightly believes he's been dubbed a liar in all this.

"The bloke has enormous pride and integrity of his values."

Butters, charged with using abusive and insulting language towards an umpire, was fined $1500 by the AFL tribunal on Tuesday.

Written reasons for the verdict are being considered by Port on Wednesday before lodging an appeal.

The tribunal sided with field umpire Nick Foot who alleged Butters said: "How much are they paying you?" after he awarded a free kick to St Kilda in Port's 14-point loss on Sunday night.

Butters vehemently denied that comment, insisting he said: "Surely that's not a free kick".

Port's Brownlow medallist Ollie Wines, who was in the vicinity of Butters at the time of the incident, testified in support of his teammate's account.

AFLPA chief executive James Gallagher said the organisation was "deeply disappointed" by the tribunal outcome.

"A misunderstanding about what was said on field should have been resolved in the aftermath of the match, not referred to the tribunal," Gallagher said in a statement.

"The tribunal determining not to accept all of the evidence consistent with Zak's version of events, including testimony of Zak's teammate Ollie Wines, nor have sufficient doubt when upholding a charge is deeply concerning.

"We've offered our full support to Zak and Port Adelaide in exploring their options to appeal."

Complicating the matter was the entire verbal exchange was not picked up by umpire Foot's microphone - though some comments before and after were.

The flashpoint came when Foot paid a free kick to St Kilda's Mitch Owens, prompting Port's Wines and Butters to protest.

Butters, who is a free agent at season's end and weighing multi-million dollar offers from rival clubs from his native Victoria, was penalised 50m and reported for abusive language by Foot.

"The comment that Butters made to me was "how much are they paying you?" Foot told the tribunal.

Foot interpreted "they" as being "the St Kilda Football Club or someone involved with St Kilda".

"It questioned my integrity," he said.

"I'm 100 per cent adamant that those are the words Zak Butters said to me."

But Butters said he was "100 per cent sure" he did not say "how much are they paying you" to Foot.

"I recall saying 'surely that's not a free kick'," Butters told tribunal.

"It hurts me because I know I didn't say it."

After the hearing, Butters told reporters: "Incredibly disappointed with the result tonight.

"I stand by knowing what I said and what I didn't say, especially what I didn't say."