FREMANTLE coach Ross Lyon denies the club's culture has been eroded by a series of off-field incidents, but says he's not in a position to speculate on the futures of Michael Johnson and Shane Yarran.

Yarran's future is hanging by a thread after being charged with assault and unlawful wounding over two separate incidents, while Johnson is facing an assault charge over a scuffle in a kebab store.

Star recruit Harley Bennell also hit the headlines for all the wrong reasons last week when his car was impounded after police discovered he was driving with an expired licence.

Lyon insists the culture of the club is still strong, but says he can't make further comment on Johnson and Yarran while their cases are before the courts.

"Everyone's allowed due process and natural justice, so it would be remiss of me to speculate," Lyon said after the team's photo shoot on Tuesday.

"I've been here five years now. Clearly I've heard the headlines thrown about culturally. But cultures are built over a long period of time.

"For four and a half years basically we were pretty much - for want of a better term - incident free.

"But certainly in a period in the off-season there's been a couple of situations that haven't pleased us.

"Clearly there's boundaries in society that if you have alleged to have broken, it escalates well beyond us.

"Our basic premise is you know right from wrong, and civility costs nothing."

Lyon said the club's leadership group, headed by captain David Mundy, was in a good position to take a strong stance on any misbehaving players.

But he doesn't think Johnson's presence in the leadership group meant any of those messages would be eroded.

Bennell flew to Germany earlier this week to seek treatment on his troublesome calves.

The 24-year-old midfielder is yet to play a senior game for the Dockers, and rumours about his off-field lifestyle are starting to surface in Perth.

Lyon said Bennell's past misdemeanours at Gold Coast meant such talk was inevitable.

"You make your bed and you lie in it. Clearly, he's had a chequered history previously," Lyon said.

"It doesn't take much to catch fire. We understand that."

Lyon was in America taking part in a leadership course at Harvard University while most of the recent drama unfolded at Fremantle.

He said some of the concepts he learned in the course could be applied to the current situation at Fremantle.

"You can do 98 good things, and if you do two things that don't look great, human nature is to focus on the bad," Lyon said.

"So what I'm here to tell you is there's 98 per cent going right here. They're vibrant and training hard."