Star North Melbourne midfielder Ben Cunnington is recovering with the support of his family after undergoing surgery to remove a testicular tumour this week.
Scans on Monday discovered the small tumour and it was removed on Tuesday.
The Kangaroos revealed the shock news on Wednesday afternoon, and they are yet to set a timeline for Cunnington's playing return.
The 30-year-old tallied 27 disposals and nine clearances in North Melbourne's upset 39-point win over Carlton on Saturday.
Just two days later, Cunnington underwent scans and the tumour was discovered.
"This has all happened very quickly, but our focus is on Ben and his family right now as they deal with this news and allow him to recover fully," Kangaroos general manager of football Brady Rawlings said.
"From the diagnosis earlier in the week up until this point, we've moved quickly to ensure Ben is in the right hands medically and that he and his family have the right support around them.
"We ask that everyone respects Ben and his family's privacy as this is a private health matter."
GWS forward Jesse Hogan, Port Adelaide star Robbie Gray, and Carlton co-captain Sam Docherty all made full recoveries after suffering their own testicular cancer scares in recent years.
Hogan, who was with Melbourne at the time, missed rounds 8-15 in 2017 after undergoing surgery to remove a cancerous tumour.
Gray was diagnosed after the 2017 season ended and underwent surgery.
Docherty recovered strongly after undergoing surgery to remove a malignant testicular tumour late last year.
Australian Associated Press