AL WAKRAH, Qatar – They were, in the eyes of some, just not good enough to make any discernible impact at the World Cup.

But an Australia side, bereft of star names that their previous squads boasted, relied on old-fashioned hard work and grit to squeeze into the last 16 after a 1-0 win over Denmark in their Group D match at the Al Janoub Stadium on Wednesday.

A second-half goal against the run of play by Mathew Leckie meant the Socceroos became the first Asian Football Confederation (AFC) nation – they left the Oceania Football Confederation in 2006 – in Qatar to advance to the knockout stages and joined France, who had already progressed after winning their first two games.

The defending champions, who fielded a second-string side, slumped to a 1-0 defeat by Tunisia in the other group game played at the same time, some 25km away at the Education City Stadium. Antoine Griezmann thought he had cancelled out Wahbi Khazri’s second-half goal, but the Frenchman’s injury-time effort was ruled out by the video assistant referee.

The result proved academic. In fact, Australia, who are 28 rungs below the 10th-ranked Danes, could have progressed with a single point, if France had avoided defeat. Conversely, Denmark could have progressed had they beaten Australia and Tunisia lost.

With margins so fine, outside the sleek Al Janoub Stadium, whose smooth curves and sheer size resemble a spaceship, there was a restlessness to pre-game festivities that was different to those in earlier group-stage matches. Speakers still blared music, smiles were still exchanged and selfies shared among fans, but the air was thick with tension. On the pitch, it was the same.

The Australians trotted out for their warm-ups about 15 minutes earlier than the Danes, and in their green, patterned pre-game kit looked more like soldiers preparing for battle than footballers preparing for a game.

They were seeking a place in the knockout phase of the World Cup for only the second time, after their last-16 showing in 2006.

That was the peak of the country’s “Golden Generation” of footballers, which was led by the likes of Mark Viduka, Harry Kewell and Tim Cahill. Nearly two-thirds of their 23-man squad at the 2006 World Cup were plying their trade in Europe’s top five leagues.

The present squad have only two: Ajdin Hrustic (Hellas Verona, Italy) and Awer Mabil (Cadiz, Spain), although Central Coast Mariners maverick Garang Kuol will join Premier League side Newcastle in the new year. In any case, they all started on the bench against Denmark.

Graham Arnold’s current squad lack a player with the style and panache Kewell displayed, or the combination of timing and nose for goals Cahill had.

But they have right-back Milos Degenek, a former refugee who fled from Serbia with his family aged six, who appeared to have no regard for his own well-being when he thrust himself in front of Jesper Lindstrom’s goal-bound shot in the 10th minute.

They have Riley McGree, the forward who chased down his own flick-on header only to have the ball smashed into his face by a Danish defender attempting a clearance, but then proceeded to chase that wild rebound too.

And they have Leckie, who, on his day, can produce a match winner out of nothing like he did against the Danes.

All the Australian players were in their own half repelling a Danish attack – as they did for most of the game – when the 31-year-old forward raced half the length of the pitch and fired a low, precise shot beyond the diving goalkeeper Kasper Schmeichel in the 60th minute.

“I’m proud, exhausted, everything really. It’s hard to describe the emotions right now,” Leckie told Australian broadcaster SBS after the game.

“We always knew we could do it as a group. We had our doubters but our spirit, our belief, our work ethic and how close we are as a group shows on the pitch.

“The last 15, 20 minutes we battled until the end. It didn’t matter what they threw at us, we weren’t conceding. We’ll make the most of it tonight, but then it’s all about recovery.”

Despite Denmark pushing desperately for an equaliser – even sending Schmeichel up for a corner – Arnold’s hard-nosed side held firm, as they have all tournament.

“We’ve been working on this for 4½ years, and I could see in their eyes they were ready tonight,” said coach Arnold, whose men will meet the Group C winners next.

“No celebrations tonight! That’s why we won after a great win against Tunisia, no celebrations, no emotion, sleep and no social media.”

The Class of 2006 may have been Australia’s Golden Generation. But now, they have their Grindin’ Generation.