The Dutch coach was part of Bert van Marwijk's Socceroos staff at the 2018 World Cup, having previously worked with the manager at Hamburg and with the Saudi Arabia national team. He arrived in Australia with only a short period to prepare the team for Russia, but left with a lasting impression of the country's football culture and the players it continues to produce.
Coumans' experience also gives him an unusual perspective on Australia's place in Asian football.
Football is not Australia's dominant sporting code, but that has not stopped the Socceroos from becoming one of the most consistent national teams in the region.
“I think Australia is a great country, but football is not the number one sport there," Coumans told Football Presse.
“You have Australian Rules, you have cricket, you have rugby. There are different sports that are bigger than football.
“But football is developing. The league is improving and you see many Australian players playing in England, Scotland and other countries in Europe.”
That overseas pathway is one of the defining characteristics of Australian football.
Players from the current Socceroos generation are spread across European and Asian leagues, gaining experience in different tactical environments and competing at levels that have helped strengthen the national team.
For Coumans, that international experience is important because it exposes Australian players to different demands.
It was something he saw first-hand during his time with the national team.
Australia's preparation for the 2018 World Cup was also unusual. Van Marwijk took charge after qualification had already been secured, leaving the coaching staff with a relatively short period to prepare the team for the tournament in Russia.
Coumans was part of that process and experienced the demands of international football with a squad representing a country whose football culture differs considerably from that of Europe.
He believes Australia's regular presence at the World Cup says something important about the country's football system.
“Australia is one of the strongest teams in Asia and I think they will stay one of the strongest teams in Asia.
“If you look at how many times they qualify for the World Cup, that shows something.
“They have good players and they have players playing at a good level in Europe, so I think they will continue to be a strong football country.”
Australia has now qualified for six consecutive World Cups, a run stretching back to Germany in 2006.
That consistency is particularly notable given the sporting landscape Coumans described.
Australia's football story has never simply been about dominating domestically. It has also been about developing players capable of moving into stronger overseas competitions and maintaining a national team capable of competing internationally.
Coumans sees that pathway as an important part of Australia's strength.
“The local league is getting better, but I don't follow it that closely anymore.
“You have many Australian players in England, in Scotland, in Europe. They get experience at a high level and then they bring that experience back to the national team.
“I think Australia will always be one of the strongest teams in Asia.”
The Australian domestic game, meanwhile, continues to occupy an unusual position.
The A-League has developed considerably since Coumans' time in the country, but it still operates in a sporting market where Australian Rules football, cricket and rugby have enormous established audiences.
For Coumans, that does not necessarily prevent football from continuing to grow.
The evidence is visible in the number of Australian players who have established careers overseas and then returned to the national-team environment with experience of European football.
That pathway has also helped Australia remain competitive against the strongest nations in Asia.
Coumans experienced that first-hand during the 2018 World Cup cycle, but his assessment extends beyond one generation of players.
The Socceroos have continued to qualify for the world's biggest tournament, while Australian players remain present throughout European football.
For a country where football competes with several deeply established sporting codes for attention, Coumans believes that consistency should not be underestimated.
“Australia is a great country and I really enjoyed my time there.
“Football might not be the number one sport, but the country has good players and they continue to develop.
“If they can keep sending players to Europe and those players keep getting experience at a high level, Australia will remain a strong team in Asia.”
Speaking exclusively to Football Presse, Coumans offers a perspective shaped not by watching Australian football from afar, but by being inside the Socceroos setup.
His conclusion is straightforward: Australia does not need football to be the country's biggest sport to remain an important football nation.
The continued flow of players into Europe — and the regular presence of the Socceroos at the World Cup — has already given Australia a place among Asia's established football powers.