The injury rules Arzani out of Australia's Asian Cup defence next January and the rest of the European season, where he is on loan at Celtic.

"This is also a very tough time for me as I received the bad news today that I will indeed need an ACL op (operation)," Arzani posted on Instagram on Tuesday after visiting a knee specialist in Spain.

The 19-year-old rising star was hurt when his knee twisted while changing direction 20 minutes into his Celtic debut last week.

Initial fears of a torn ACL were confirmed when Arzani visited world-renowned knee surgeon Ramon Cugat in Barcelona.

Cugat has treated numerous high-profile players including Manchester City's Kevin De Bruyne, Brazil striker Gabriel Jesus and Argentine ace Sergio Aguero.

Arzani will have soon have a knee reconstruction, which usually requires at least nine months of rehabilitation.

"Thank you to everyone who has taken the time out of their day to show support and love," Arzani wrote.

" ...This is however the beginning of my journey and I promise to be back better than ever. Day 1 road to recovery starts now."

Australian Associated Press