For anyone doubting Ange Postecoglou's ability to turn Celtic around, they only need to talk to former Brisbane Roar captain Matt McKay.
The former Socceroo was at the heart of a Roar team Postecoglou successfully transformed into two-time A-League champions a decade ago.
Much like his reign so far at Celtic, Postecoglou's tenure as Roar coach began in shaky fashion after arriving 10 games deep into the 2009-10 season.
The Aussie coach lost his first two games, only won two of his first eight matches and saw Brisbane suffer a humiliating 5-1 defeat against local rivals Gold Coast United.
Postecoglou's side ended the season in second last and one point shy of a dreaded wooden spoon.
But with a full pre-season to work with, the next campaign saw Postecoglou turn the club around in drastic fashion as they finished the regular season in first before staging an incredible comeback to win the grand final against Central Coast Mariners having been 2-0 down in extra time.
McKay saw the club's transformation first hand and detailed how Postecoglou simply needed time to enact successful change.
"He came halfway through a season and it wasn’t until the next pre-season that he really put a stamp on how things were run and our style of play," McKay told Sporting News.
"But once he did that, he got his players in and he could really work his magic.
"To be honest, that first day of pre-season I went in not expecting much. It was my last year on contract and I was planning on leaving after that, but he turned the place around.
"He motivated, got his point across, had us playing great football, it was really enjoyable to come to training, we went into games knowing you were going to win.
"You can speak to any footballer, when you’re positive and high on confidence, you tend to win games and he really helped with that at Brisbane."
Postecoglou has won nine of his first 18 games in charge of Scottish giants Celtic - a ratio many fans believe simply isn't good enough for a club of their stature.
But McKay is adamant that, like his old Brisbane side, the Hoops are on the right track to long-term success with the Aussie at the helm.
"I can’t speak highly enough of him. As you can already see, the way they’re playing, he’s already put his stamp on it," McKay said.
"It seems like the players are buying in to that. Obviously they lost a few in the transfer window and the nature of turnover in players means it will take time.
"The signs are good. The results will come and the team will get better. I think it’s great for Australian football that he’s over there."
McKay's short spell in Scotland
While most of McKay's playing career was spent with Brisbane Roar, he enjoyed a brief stint in Scotland with Celtic's fierce rivals Rangers in late 2011.
Though his European adventure was restricted to just three appearances, the now 38-year-old has no regrets about the experience.
"I had to go. Maybe it wasn’t a great fit for me but I was 28, didn’t have a European passport, fought my way into the national team and got my opportunity there which I was very grateful for," he said.
"It’s a massive club with great people but it was the wrong time for the club unfortunately. I was one of their last signings and then when the club went into administration, I was one of the first to go.
"I loved it though. Was only seven months but was great to go to a country where football was number one and got to live and breathe it."
Since hanging up the boots in 2019, McKay has found unexpected success with a baby business he launched with his wife after having their first child.