Heading into night four of the FIBA Women's World Cup there was a sense of the Opals needing to show what they really stand for after a rough opening night loss to France, before bouncing back with a monster win over Mali.

Which Opals team would show up? The good or the bad?

Well, it didn't take long to realise that the Opals meant business against Serbia in front of over 9,300 fans on Sunday night, and it was all off the back of manic defensive intensity and energy which was on display in the opening minutes.

They answered every challenge Serbia – a real rival of the Opals – threw at them on their way to a rousing 69-54 win.

With the well-deserved insertion of Marianna Tolo into the starting five, Australia boasted more strength and grunt in the paint from the outset and it paid dividends with the defence being absolutely on point, forcing Serbia into positions they didn't want to be in on the court.

Australia's defensive intensity was on another level and Serbia was turning the ball over under constant pressure, which led to great offensive looks for the Opals.

After hitting a tournament-high 18 triples in their previous game against Mali, it would've been easy for Australia to fall in love with long-range shots to open the game against Serbia.

But it was great to see they drove to the bucket early – led by Sami Whitcomb – to open up space on the perimeter and work into three-point attempts as the game opened up.

While there were plenty of moments that stood out defensively for the Opals in the first quarter, including forcing an incredible four Serbian shot clock violations, a play by Kristy Wallace in the final two minutes of the term truly set the tone for the Opals for the remainder of the game.

When she really had no business in doing so, Wallace stood up to Katarina Zec at half court with her signature defensive pressure and drew an offensive foul.

In that moment, Wallace sent the Australian fans and her teammates in raptures, especially captain Tess Madgen who immediately ran over to Wallace to praise her determined work.

Plays like that do so much for an entire team and it was clear that the Opals lifted with Wallace's presence on the court.

Dennis Denuto in the classic Australian film The Castle said it best; "it's the vibe of the thing" and the vibes inside the Sydney Superdome were absolutely electric. With every Serbian turnover caused by the hectic Australian defence, the crowd got louder and louder.

Every Opal was playing inspired basketball on both ends of the court, including Lauren Jackson who again provided an incredible lift off the bench with five first-quarter points.

Meanwhile the play of Bec Allen – who heartbreakingly went down with suspected broken ribs in the final minutes of the game – was simply extraordinary with her length causing havoc on the defensive end.

Australia took lessons from their loss to France and applied them against Mali on Friday night, but applying those same lessons against a medal contender like Serbia should provide so much confidence to the team.

Like any good team, Serbia responded after a slow first quarter by coming out with renewed vigour in the second quarter to trim the margin back to only three points, 18-15.

This signalled another test for the Opals and to their credit, they responded with another burst of defensive energy and the shot-making of Allen was absolutely elite in returning the momentum back to Australia.

Coach Sandy Brondello spoke before the tournament about defence being the calling card for the Opals and that's exactly what was key to setting alight their offence against Serbia.

The relentlessness of the Opals outlasted the physicality of the Serbians and that isn't an easy thing to do.

The first five minutes of the third quarter were the perfect example of what the Opals were all about – they held Serbia scoreless until the 5:10 mark of the term and whenever Serbia challenged or looked capable of making a run, Australia came up with a big bucket from the likes of Sami Whitcomb, Jackson or Allen.

The most dangerous Serbia looked was when they were applying a full-court press and this has been an issue the Opals haven't really been able to find an answer for in recent times.

Those issues did arise again for the Opals – mainly in the second half – as turnovers mounted, but as I mentioned earlier, timely buckets by Australia's stars kept Serbia at bay.

Serbia's physicality did worry Australia at times, but the Opals never lost their heads and remained composed, which wasn't the case against France earlier in the tournament.

This shows Australia's growth in just a matter of days and great maturity to be able to implement lessons learnt so quickly.

Whitcomb's game was far from perfect, highlighted by seven turnovers, but you simply can never fault her effort and the passion she plays with.

You can live with mistakes if there's a clear desire to play the right way and Whitcomb typifies what the Opals have long been known for – toughness and grinding out wins by any means necessary.

In one of the highlights of the game, Whitcomb grabbed a steal on the defensive end with blood dripping from her nose and she was then seen celebrating an Ezi Magbegor bucket from the bench while still being attended to by medical staff.

Now three games into the tournament, the Opals have a clear identity and that's an incredible turnaround after what was a disheartening loss to open a World Cup campaign on home soil against France.

The Opals have found what works for them; manic defensive pressure and feeding off that to create an offence that moves the ball.

In the five or so minutes they went away from that in the third and early fourth quarters – when Serbia lifted their defensive intensity – things went south for Australia because they weren't moving the ball, nor were they helping the ball-handlers elude defenders by setting screens.

Setting a good, strong screen is one of the most underrated aspects of basketball and bigs like Jackson, Tolo and Cayla George are all fantastic at that, but when the ball-handlers are getting hawked by defenders the length of the court, those bigs need to get into the back-court and set a screen to get them free.

Despite those issues surfacing again, it was a game that showed Australia's toughness and heart. They wouldn't be denied or bullied by Serbia's physicality and when the Opals play like that, they look like a team capable of competing for a podium finish.