The four-time premiership player had an extended break during the pre-season because of his father's ill health.

This break will also be indefinite and teammate Shaun Burgoyne said the Hawks will give the star forward whatever time he needs.

"He'll take his time up there dealing with that and when he returns, I'm not sure when that will be," Burgoyne said.

"I'm not too sure, to be honest - it's just a private matter.

"The club always, with every player who's had a private matter, they give them the time to deal with it and they come back.

"So there is no timeframe."

Rioli has not played since round four because of a knee injury and also missed a big chunk of last season with a knee problem.

"We're always a better team when Cyril plays," Burgoyne said.

"He's had a horrible run with injuries of late, so we'll just have to deal with that."

The 28-year-old is one of the Hawks' most important players and won the 2015 Norm Smith Medal for his performance in the grand final win over West Coast.

In February, after he had returned to the club, Rioli said he contemplated early retirement while on leave in the Top End.

Cyril Snr needed surgery last year after suffering a near-fatal heart attack.

In late 2016, Rioli re-signed with the Hawks until 2020.

He had trained well in the last few weeks and was on target for an AFL return.

Burgoyne said he speaks with his fellow indigenous star regularly.

"He was flying on the track," Burgoyne said.

"Cyril doesn't fluctuate too much, he's a pretty humble and shy type of guy.

"He keeps very grounded."

The Hawks said in a statement on Tuesday that Rioli had returned to Darwin with wife Shannyn, to be with their family.

"Physically, Cyril is in great condition, and potentially could have played for us in the coming weeks. However, we acknowledge his desire to be with family," Hawks football boss Graham Wright said in a club statement.

"Our priority at Hawthorn is our people and we ask that Cyril's privacy be respected at this time."

Rioli has played 189 AFL games for Hawthorn since his 2008 debut.

Australian Associated Press