And a lot on his mind he surely has.

From Tuesday morning, the High Court will sit in Canberra to decide whether to relieve Canavan of those mental burdens - taking a lot off his mind by removing everything from his plate, namely his entire senatorial career.

But as the citizenship debacle approaches its judicial climax, the senator and erstwhile minister was front and centre at the ABC's Melbourne studio for the weekly round of domande e risposte.

Pretty much everything sounds better in Italian - everything except Matt Canavan's career - but as those questions and answers came thick and fast, Canavan often settled for blunt, plain English as he engaged in a series of snippy and snappy jousts with Greens leader Richard Di Natale.

"What a load of rot," Canavan declared at one point.

"Rubbish," he proclaimed at another.

A word he didn't say? "Adani" - even though that was the controversy-plagued project about which he was quizzed by an audience member who recognised the elephant in the room.

"Should the High Court rule on your citizenship issues in your favour and you return to your role as resource minister??? will you continue to advocate to loan Adani $1 billion of taxpayers' money, despite all the evidence that proved the Carmichael coal mine is economically unviable, that Adani will deliberately attempt to not pay any tax, will seek to automate all the jobs away, and leave a devastating wake of environmental destruction?"

Well, when you put it like that???

A minister on enforced sabbatical has to find a way to answer that hits all the right notes but avoids all the wrong words. Like "Adani" and "$1 billion of taxpayers' money". Instead, Canavan waxed lyrical about the "opening up of the Galilee Basin" - it definitely sounds better - and rosy job prospects and following the wishes of the traditional owners.

It all sounds??? bellissimo.

Or not, as Di Natale - wearing a Stop Adani t-shirt - was keen to point out.

"The reality is if this mine goes ahead, we lose the Great Barrier Reef," he began.

Canavan declared this to be "rot" but Di Natale wasn't deterred, calling Adani a "multinational tax dodger on steroids" and clearly relishing being able to rub his rival's nose in the details of a project that stinks to high heaven.

There were clashes on other topics - the same-sex marriage debate naturally produced the widest gulf, with Canavan holding firm in the No camp and Di Natale poking Tony Abbott in the eye with a riff on the NRL grand final.

Canavan: "We should all be able to express our views and debate is a wonderful thing."

Di Natale: "I know Tony Abbott would have preferred Onward, Christian Soldiers to Macklemore's Same Love, but the good news is lots more people got to hear it. I reckon some of the most powerful moments are when sporting people stand up and take a stand."

Which brings us to the evening's most refreshing guest, making her Q&A debut: Peggy O'Neal, CEO of the AFL premiership club Richmond, who had thoughtful contributions on that very question of mixing sport and politics.

Tony Jones asked: "You're an American, originally at least. What did you think when Donald Trump came out and said if it was up to him he would sack ... players who took the knee in protest over police killings of young black men??? during the national anthem?"

O'Neal traversed the Trump minefield with aplomb.

"One, I'm glad he's not the owner of all those teams, but I think it also shows there's solidarity among teammates whether you're black or white??? There are people from all walks of life taking the knee to show solidarity, that you can't ignore the fact of our history, you can't ignore slavery or racism," she said.

"I think it's now in a public debate and Donald Trump is very divisive. His actions allowed more people to stand up and say, 'I'm with them'."

Later, she noted that sports people had every right to express their views, no matter how controversial - but that they also had to expect the public to mark them up or down on those views as they saw fit.

"That's the accountability part," she said.

"Think of Muhammad Ali now and he was very decisive back then. He was an Olympic gold medallist and decided he didn't want to go to Vietnam. He lost that and went to prison. Then he came out as a civil rights leader.

"[Athletes] don't always say what the majority of the community wants. But they are connected to community. And they often do reflect community values because sporting clubs are not separate to community."