The father of Angus Crichton has spoken out following his son's absence from the Sydney Roosters trial, revealing the Kangaroos' back-rower has been diagnosed with bipolar disorder.

The 27-year-old forward, coming off the back of a World Cup victory, has been granted indefinite leave from the club following the diagnosis, with no timeline set as of yet for a return to the field.

News Corp reported earlier in the month that he'd stepped away from pre-season training issues and didn't attend the Roosters' annual off-season training trip to Queenstown, missing both trial matches as a result.

Angus' father, Charlie Crichton, released a statement to Nine News revealing his son's status.

“I can confirm today that Angus is under appropriate professional support and treatment for medically diagnosed bipolar disorder which he has been dealing with for some time,” Charlie told the program.

“He is fully supported by his family, his management and the Sydney Roosters club as he works toward recovery.

If you need help in a crisis, call Lifeline on 13 11 14. For further information about depression, contact beyondblue on 1300 224 636 or talk to your GP, local health professional or someone you trust.

"While no timeline has been set for his return to rugby league, we will continue to trust his medical team and know those within the rugby league community will respect his right to privacy.”

It's a blow for the Roosters on the field, who are already without fellow back-rower Sitili Tupouniua as he recovers from an ACL injury, while both Joseph Manu and Luke Keary are in varying levels of doubt for the opening round.

Connor Watson and Billy Smith are also currently in the club's injury ward.

Crichton's absence opens the door for Fiji international Siua Wong to debut against the Dolphins after showing glimpses of immense talent in the World Cup as well as the trials.

NRL Rd 4 - Roosters v Warriors
SYDNEY, AUSTRALIA - APRIL 04: Angus Crichton of the Roosters is tackled during the round four NRL match between the Sydney Roosters and the New Zealand Warriors at Sydney Cricket Ground, on April 04, 2021, in Sydney, Australia. (Photo by Jason McCawley/Getty Images)

The back-rower's mental health is the key focus for both his family and the club as Angus comes to terms with the diagnosis, with no emphasis or rush for the 27-year-old to return to the playing field.

The New South Welshman recently re-signed with the Roosters through to the end of next season, joining Victor Radley, who has also put pen to paper on an extension in Bondi.

If you need help in a crisis, call Lifeline on 13 11 14. For further information about depression, contact beyondblue on 1300 224 636 or talk to your GP, local health professional or someone you trust.