ADELAIDE midfielder Matt Crouch is under police investigation for an incident with a Port Adelaide supporter as the bitter fallout from last weekend's Showdown continues.

Crouch flicked the cap off a Port supporter's head when exiting Adelaide Oval after his side's 22-point loss.

The Power supporter, who was leaning over a boundary fence and yelling at Crows players as they left the field, reported the incident to police.

"It's one I can't comment around, there's an investigation going on at the moment, but Matt has got our full support," Adelaide coach Matthew Nicks said on Wednesday.

SA Police confirmed an investigation was underway following a complaint from the Port supporter.

The Crouch incident follows Port defender Dan Houston being banned for five games for a bump which knocked out Adelaide's Izak Rankine in the match won by the Power. The Power announced on Wednesday they will challenge the length of the ban at the AFL Appeal Board later this week.

Port's mascot was also struck in the head by a young Crows fan before the game, suffering a bloodied nose. No action was taken because the Adelaide supporter is a minor.

Power forward Willie Rioli was also racially abused online following the game in an act condemned by both clubs.

Crouch was involved in several on-field skirmishes with Port Adelaide players during the game.

In the aftermath, footage shows the Port supporter leaning over a fence and yelling at Crows players as they exited through the players' race.

Crouch, not breaking stride, flicked the cap off the fan's head.

"It's a hard one ... the reason that we, I guess, allow fans close to the boundary line is for those kids that just love footy," Nicks said.

"They have idols and they have heroes and they want to come down and get amongst it and (take) selfies and that's the really positive part of our game that we love."

Asked if a proverbial line had been crossed, Nicks replied: "It's just passion for sport.

"It was a big week, a big Showdown.

"We played against a side that were playing for top two, top four, playing for finals; the competition is so tight so it was a huge game.

"And with that comes an intensity, the intensity I think we all enjoy and love.

"When adrenaline is pumping and emotions are high, sometimes we can overstep the line and it can happen to anyone.

"Yeah, some could argue there was a little bit of that on the night."

Post-match, Nicks was captured by television cameras in what appeared to be a heated discussion with Port coach Ken Hinkley.

"Apparently someone was lip-reading ... but I don't need to share everything that we spoke about," Nicks said on Wednesday.

Nicks refused to be drawn on Houston's five-match ban.

"Izak ... we're pleased with how he's recovered, initially it was a bit of a concern on Saturday night," he said.

"But he's in pretty good spirits and that's really the only concern I've had out of it all.

"With respect, I don't care what the punishment is. It doesn't interest me.

"I'm interested in ... our players, their welfare, their health."