An AFL premiership coach has earned a spot in Jannik Sinner's box for Sunday night's Australian Open final.

The fourth-ranked Sinner will battle Russian Daniil Medvedev, third-ranked, at Rod Laver Arena for the 2024 Australian Open title.

And, in his coaches' box will be former Port Adelaide senior coach Mark Williams.

Williams, who coached the Power to its only AFL premiership in 2004, has maintained a close relationship with Sinner's coach, Darren Cahill, through their fathers and the Port Adelaide Magpies.

MELBOURNE, AUSTRALIA - AUGUST 3: Warren Tredrea #16, Gavin Wanganeen #4 and Mark Williams coach of Port celebrate winning the round 18 AFL match between the Hawthorn Hawks and the Port Adelaide Power at the Melbourne Cricket Ground August 3, 2003 in Melbourne, Australia. (Photo by Mark Dadswell/Getty Images)

In addition to head-coaching at Port Adelaide, Williams has assistant-coached at Essendon (1995-96), GWS (2011-12), Richmond (2013-16) and has been at Melbourne since 2020, and also coached Werribee in the VFL between 2019-20.

Williams' father, Fos - an iconic South Australian football figure - coached Cahill's father, John, at the Magpies.

Darren, who joined Port Adelaide's board in 2018, in his own words learned "95 per cent" of his coaching expertise while at Alberton.

"95 per cent of my coaching throughout my entire career was learnt through the Port Adelaide Football Club," Cahill said, via News Corp.

"It's just what I was brought up with, with my dad coaching there for so many years and being successful.

"There are some habits and some cultures and some ways of coaching that never leave you."

John, who coached Collingwood in the VFL from 1983-84, appointed Mark captain of the Magpies, while, meantime, Darren played tennis professionally.

Cahill has been coaching Sinner since July 2022 when he joined Simone Vagnozzi in leading the prodigious Italian.

Sunday's deciding match between Sinner and Medvedev is scheduled to start at 7:30 PM AEDT.