Former Brisbane Roar skipper Matt Smith reckons Celtic supporters were gripped by the fear of the unknown when Ange Postecoglou was appointed as the new boss last summer.

But the defender insists that the Hoops boss has been on an incredible journey in his life as well as his career - Parkhead was simply his next destination for success. 

The ex-Roar skipper won back-to-back A-League Grand Finals under Postecoglou in 2011 and 2012, the only Australian side to achieve that feat to this date.

The duo also embarked on the biggest unbeaten run in Australian team sports history after going 36 games without defeat in 2010 and 2011. 

Nobody is more delighted than Smith that Postecoglou has also kept up his habit of winning league titles in Glasgow's east end after guiding Celtic to a Scottish Premiership and League Cup double last season.

His former captain insists that, quite simply, 56-year-old Postecoglou will always strive to be the best coach that he can be.

READ MORE: Brisbane Roar, Celtic Thunder - A front-row seat to Ange Postecoglou's Australian sporting history

Smith, now 40 and player/coach at Brisbane City, said: "When Ange Postecoglou got the opportunity to go to Celtic from Japan it was a definite case of a fear of the unknown.

"His appointment scared people too much. I remember doing interviews at the time and I told all the Celtic supporters who would listen 'don't judge Ange at the beginning, judge him at the end'.

"Because what a journey Ange has had. His whole coaching journey and life story is a phenomenal one.

"With Ange, he is a very ambitious coach and he himself always wants to be the best that he can be. He loves the challenge. He is constantly pushing himself and he has the drive to try and be the best.

"When we [his former Roar players] saw him with all of his family on the pitch during Celtic's title celebrations back in May, it was just so very pleasing to see."