In the week leading up to Australia’s first Olympic qualifying play-off match against Vietnam, head coach Ante Milicic said his team had been addressing what has become a characteristic strategy deployed by many of their Asian opponents: deep, compact defensive blocks.

This strategy almost saw the Matildas’ 2019 World Cup hopes dashed when they faced a stoic, counter-attacking Thailand side at the 2018 Asian Cup. Though they were mistake-prone, Australia struggled to cause fractures and open up space within Thailand’s two tight banks of four.

Australia 5-0 Vietnam: Olympic qualifying playoff first leg – as it happened Read more

The same strategy also could have seen the Matildas enter an Olympic play-off against a strong South Korean outfit, were it not for Emily van Egmond’s stoppage-time strike that earned a draw against a well-drilled Chinese team last month. While Australia dominated the ball that game, it was China that dominated the space off it.

Although Vietnam didn’t pose the same physical or technical challenges in Newcastle on Friday night as China did, Australia’s 5-0 win showed one important facet that they’ve sharpened when it comes to breaking down these deep defensive units: the role of the full-backs.

Steph Catley and Ellie Carpenter have been two of the Matildas’ unsung heroes in the team’s most recent international fixtures. Catley created three goal-scoring opportunities and contributed one of the seven goals against Taiwan in Australia’s opening qualifier, while Carpenter dominated in the second against Thailand, notching two assists and creating six chances on goal; second in influence only to Van Egmond, who was awarded player of the match.

Against Vietnam it was just the second time the two full-backs were deployed together during these qualifiers and it was clear from the opening whistle how much of an extra dimension they offer, particularly when Australia’s more recognised central weapons like Sam Kerr and Caitlin Foord struggle to be involved in attacking moves.

Hugging their respective touchlines to pull their opponent’s back four apart, both Catley and Carpenter’s positioning often forced Vietnam to change shape. Several times, the visitors dragged a midfielder deeper to create a back five and crowd out the central channels where Kerr and Foord were often lurking, which just created more space, and hence more opportunities, for Australia’s midfielders – where two of the five goals came from.

Despite Milicic’s pre-match warning of Vietnam’s back five, the strategy was a largely futile one as Carpenter and Catley ran riot down their respective wings. Both full-backs easily added to their assist tallies in the first half, with a fizzing cross from Carpenter meeting the head of Kerr for the opening goal in the ninth minute, while a cross from Catley was met by Van Egmond who headed home the Matildas’ third in the 37th.

Facebook Twitter Pinterest Steph Catley on the way forward at McDonald Jones Stadium. Photograph: Darren Pateman/EPA

In total, the two full-backs were two of Australia’s most influential attacking threats behind only Van Egmond and Foord for combined chances created. Both also led the field in tackles and duels won alongside centre-back Alanna Kennedy. “We’re another outlet,” Catley told Guardian Australia post-match. “When a team is in a low block like that, you need as much width as possible. Sometimes the strikers can’t always give that, and if Ellie [Carpenter] and I are able to do the job on both ends, then that really helps the team. Getting involved in the attack is something that both of us love to do and if we can help going forward and keep a clean sheet at the back, things are great.”

However, the risk posed by playing such attack-minded full-backs together is that they can be caught upfield on the counter. Indeed, the game could have taken an interesting turn after 17 minutes had striker Pham Thi Tuoi turned in a neat cross from Nguyen Thi Bich Thuy, who repeatedly found space in behind the galloping Carpenter. “When you’re in control of a game like that so much, it exposes you a little bit to those counter-attacks,” Catley said. “It’s about finding balance.”

It was a weakness in Australia’s set-up that Vietnam head coach Mai Duc Chung had identified, perhaps having seen its effectiveness in the China draw. “I recognised that the defence line of Australia is very high and [had] many space behind,” he said. “So we try to use this weakness of the Australian team, and today we had some chance but […] we cannot score.”

That the Matildas will qualify for Tokyo is in little doubt heading into the second leg. The question, instead, is the role the full-backs will play when coming up against stronger sides, and whether the system Milicic is embedding can provide this balance between attacking influence and defensive responsibilities. “When we play an opponent that potentially has more threat on the counter, we’ll look to address it,” Milicic said post-match. One hopes that Australia’s remaining games – the return leg against Vietnam as well as friendlies against the USA and Canada in April – are opportunities for him to address these details. A gold medal may be riding on it.