Ange Postecoglou arrived at Celtic with the club at its lowest ebb in over two decades.

The team had just finished 25 points behind their bitter rivals, key players appeared to be queuing up to get out the door and the fanbase was looking more and more unified against the board. Add in an ill-fated, embarrassing rejection from Eddie Howe and it’s safe to say confidence for the new term wasn’t exactly sky-high.

Yet, one year on, the league and League Cup are back at Paradise and Champions League football is coming back inside the gates of Parkhead.

One would think that it would be a tough season to replicate however, by all accounts, the Celtic support should expect even more this season. Fans in Japan and Australia alike speak of how it is the second season in which Postecouglou’s teams really get going – and it would take a brave soul to question them after the number of critics that were left red-faced following his maiden campaign double.

It is not hard to see the difference in the 56-year-old’s previous sides once they reach his second season. In the 2009-10 campaign with Brisbane Roar, Postecoglou led them to ninth place in the A-league with eight wins, 30 points and a goal difference of minus-10. The following season they finished top with 18 wins, 65 points and a goal difference of plus-32 – an improvement of 35 points.

That was also the season in which his side began what would become an Australian record 36-game unbeaten run that helped them lift two titles in the 2010-11 and 2011-12 seasons – an unprecedented feat in the A-League.

With Yokohama F. Marinos he guided the club from a 12th-place finish in 2018 with 32 points and a goal difference of zero to top of the table on 70 points and a goal difference of 30.

So, what changes does Postecoglou make in preparation for this second-season improvement?

At Brisbane Roar he brought in 14 players. Postecoglou even travelled to Europe in search of an attacking midfielder, an effort that culminated in the signing of Thomas Bruich from Nuremburg, who is now considered one of the best players in A-League history. The same number of players departed, including club captain, Craig Moore, and some of their best young players in Robbie Kruse and Chris Grossman.

He signed Kosta Barbarouses and Jean Solorzano, players who both finished the season as joint second-top goalscorers in the league.

This eye for quality signings helps his sides dominate their league. Being able to identify players that fit into his system well and will perform when needed is a trait that cannot be understated, especially at a side like Celtic where the majority of signings are arguably going to be players that most fans will not have heard of – outside scouting circles at least.

“Look at all the players he has signed, and the majority have made a real impact,” former St Mirren player Steven McGarry, who competed against Postecoglou’s Roar side during a stint with Perth Glory, told the Daily Record recently. “They have to fit into how he wants his teams to play. His teams have always played football, he likes to get the ball down and to have high energy and movement.

“When I went out to Perth Glory, he took over at Brisbane Roar and made a lot of changes in his playing staff. Craig Moore and Danny Tiatto all left. Ange came in and made his own signings and they were smart signings.

“There were Europeans who were top players for Brisbane and the A-League for two or three years. He has a real eye for a player, and he has shown that in his first year at Celtic.”

A similar effect occurred in Yokohama, as Japan Times football journalist Dan Orlowitz recalls.

“The main strategy – high pressure and high-intensity attack, lots of possession in the opponent's half etc. – didn't really change,” he told The Celtic Way. “What did change was smarter play –  fewer turnovers, better risk management and defenders who were able to stop opposing counters that often would have led to goals surrendered. Yokohama in 2018 played very interesting football but the defence was all over the place.

“I think Postecoglou is always broadly looking for the same type of player – and that's players who fit well into his system. They notably signed a great pair of Brazilian attackers midsummer – Mateus and Erik – who helped plug injury gaps (notably Edigar Junio) and really got the team over the line

Celtic Way:

“But the big signings he made for 2019 were defensive – goalkeeper Park Il-Gyu was better-suited to being a sweeper-keeper than Hiroki Iikura had been in the previous season.

“Thiago Martins was a summer 2018 signing but he proved to be very important defensively in the 2019 campaign. And then there was Theerathon Bunmathan, who wasn't always a perfect defender but his speed at left-back and ability to contribute offensively fit very well into Ange's style.”

Comparisons could be made between the description of Bunmathan, who went on to make 78 appearances for Marinos, and those of Celtic’s new left-back signing Alexandro Bernabei. The £3.75m capture from FC Lanus is reported to be a formidable threat offensively but with room for improvement defensively.

“As I think you're seeing from the signings that have been announced so far, Ange’s year two is about building on what worked last season and making improvements to areas of the squad that weren't quite as stable,” Orlowitz added. “Depth is also going to be key – now on top of all the domestic cups you've got the Champions League and that's going to test the players in ways many have never experienced before.

“I think by now, the fans know what they're getting with ‘Ange-ball’ but so do opposing teams. They're going to spend next season trying to come up with ways to stop this Celtic side – and Postecoglou is going to have to get his players to execute his strategy at an even higher level. That's the cat-and-mouse game Celtic fans get to enjoy this season, on top of a return to Champions League nights.”

While the Hoops fired on all fronts in the Premiership last season, going on a 32-match unbeaten run from October until the end of the season, there is plenty of room for improvement on the European side of things. The club hasn’t progressed through a continental knockout tie since 2004 and it is vital that the mental block is put to bed sooner rather than later.

After crashing out of the Champions League qualifiers against FC Midtjylland last season – a fixture that would’ve left neutrals praying for the final whistle – Celtic earned nine points in the Europa League group stage in a section with top-quality sides in Bayer Leverkusen and Real Betis.

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The other team in Group G, Ferencvaros, had put the Hoops out of the Champions League qualifiers the previous year. Nine points was respectable but not enough to put the club through. Interestingly, Midtjylland were the only other team to accumulate nine points and not go through to the latter stages of the competition.

After dropping into the Europa Conference League Postecoglou’s men faced Norwegian champions Bodo/Glimt, who had beaten Roma 6-1 in the group phase. Finishing 5-1 on aggregate, the tie taught Celtic that they needed to be much more disciplined and physical in midfield and that players had to be better on the ball in the defensive positions as Bodo passed out of their press effectively.

Ahead of this term’s European tilt, Postecoglou has managed to sign on both standout loanees of last season in Cameron-Carter Vickers and Jota for combined reported fees of £12.3m plus add-ons. The Bernabei addition also bolstered the defence while depth between the sticks was added with Benjamin Siegrist’s signing. Maeda’s loan also became permanent through the club’s obligation-to-buy clause in his loan deal from Marinos.

Club stalwarts Tom Rogic and Nir Bitton both left the club this summer after a combined 17 years in the Hoops. Rogic in particular is a player not easily replaced – the magic he could bring to games was a rare commodity. Bitton was effective at helping see a match out. Both are players who will be missed if the club fail to bring in a fresh face in the middle of the park.

"Look, we have to be better next year, irrespective of how we went this year.” Postecoglou said at the end-of-season Scottish Writers’ Football Awards dinner. "But the way I want teams to play and the whole training process and everything – it takes a while for people to gel with.

"I'm really hopeful that next year we will be a stronger team. We have to be – and I look forward to what that brings."

It is difficult to improve on a double in a debut season. However if fans of Australian, Japanese and Scottish football have learned anything, it’s that doubting Postecoglou is not the wisest of decisions.