Umpire Nick Foot alleged Butters said: "How much are they paying you?" after he awarded a free kick to St Kilda in Port's 14-point loss to the Saints on Sunday night.
Butters, 25, vehemently denied that, insisting he said "surely that's not a free kick".
AFLPA chief executive James Gallagher said in a statement: "We are deeply disappointed by last night's tribunal outcome for Port Adelaide's Zak Butters.
"A misunderstanding about what was said on field should have been resolved in the aftermath of the match, not referred to the tribunal.
"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."
Port will learn why Butters was found guilty, then make a call on whether to appeal that decision when the tribunal releases the reasoning behind their verdict.
The tribunal strangely set itself a 5.45pm (AEST) deadline and announced its verdict minutes before that mark, with written reasoning to be distributed on Wednesday morning.
Port released a statement on Tuesday night saying the club "stands unequivocally" with Butters, who is a free agent at season's end and has a decision to make on whether to return to Victoria.
"The club is deeply disappointed in the Tribunal's verdict and rejects any suggestion that questions Zak's integrity," Port Adelaide chief executive Matthew Richardson said.
"Zak is a man of outstanding character and we are acutely aware of the toll these proceedings take, not only for him but for his family and those closest to him."
On Sunday, a free kick was given to St Kilda's Mitch Owens and Port's Ollie Wines took issue, as did Butters, who was penalised 50m and reported for abusive language by Foot.
The AFL said the exchange was not picked up by the umpire's microphone.
"The comment that Butters made to me was "how much are they paying you?" Foot said.
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."
Butters 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 said.
"It hurts me because I know I didn't say it.
"I'm clearly disappointed with the result ... I stand by knowing what I said and what I didn't say, especially what I didn't say."
Wines and Port football boss Ben Rutten gave evidence in support of Butters.
