Australia’s Davis Cup quarter-final win against Kazakhstan was more than just a victory. It was a lesson.

But the lesson wasn’t for the brave losers – who have punched above their weight to reach the last eight of the event in four of the past five years.

It was for Nick Kyrgios and Bernard Tomic. And it was plain and clear: if you want to make it at the top level, you’re going to need more than your obvious talent.

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There could have been no better teachers than Lleyton Hewitt and Sam Groth.

The pair kept Australia – trailing 2-0 after Friday – in the tie with victory in the doubles, before they both won singles clashes on Sunday to cap a memorable come-from-behind triumph.

Hewitt, who should have his feet up in retirement, has exacted every last ounce of energy out of himself to improve his game.

The 34-year-old, on an extended farewell tour of the ATP circuit, wasn’t slated to play singles in Darwin.

Hewitt had plenty to celebrate in his straight-sets win on Sunday. Photo: AAP

But with Tomic off getting arrested in Miami after being axed by Tennis Australia, Kyrgios unable to control his on-court emotions – and letting it drastically affect his tennis – and Thanasi Kokkinakis perhaps overawed, Wally Masur turned to a man he knew he could rely on.

Hewitt’s victory in the fifth and deciding rubber of the tie against Aleksandr Nedovyesov wasn’t guaranteed.

But his effort, commitment and never-say-die attitude was.

Representing your nation, in whatever pursuit it is, is a privilege and an honour. Not a right.

Hewitt is well aware of that but you get the sense Tomic and Kyrgios haven’t quite grasped that notion.

Tomic initially threatened to boycott the tie before saying he would play out of respect for Hewitt.

But he did as much as he could – without refusing to play again – to make it impossible for Masur to select him with a tirade at Tennis Australia following his Wimbledon exit in which he aimed fire at chief Craig Tiley and director of performance Pat Rafter and certainly did not miss.

So instead of a trip to Darwin, Tomic headed for Miami.

Kyrgios, himself embroiled in incident after incident at Wimbledon, cried “I don’t want to be here” during his defeat to Nedovyesov on Friday.

Here’s a young man, who while gifted with ability, let himself down at SW19 with repeated displays of petulance. Surely he’d be keen to make up some ground with the Australian public?

But no, Kyrgios – who himself tweeted criticism of Rafter in the build-up to the tie – seemingly wished he was elsewhere. Like Miami.

Tomic was arrested after a penthouse hotel party in Miami on Wednesday.

Dropping Kyrgios on Sunday and replacing him with Groth was a Masur masterstroke.

Out went the troubled tyro and in came a 27-year-old in the best form of his life and surely pinching himself at his progress.

Just four years ago, Groth was playing Australian Rules socially after quitting tennis. When he returned to the sport, he was ranked 575th in the world – a long way away from a Davis Cup quarter-final.

Now at 68th in the rankings, Groth has enjoyed an excellent year, reaching the third round at the Australian Open and Wimbledon.

He even took a set off Roger Federer on Centre Court at the All-England Club.

That should have been making headlines – instead the circus surrounding Kyrgios and Tomic did.

Groth played superbly on Sunday, serving well in a four-set win over top-ranked Kazakh Mikhail Kukushkin that set it all up for Hewitt to play hero.

Just as important as his win was the fact he wanted to be there.

Post-match comments left us in doubt at what winning meant to Groth.

“We’ve still got one more [win] to go, but this is probably the most amazing thing I’ve ever had in tennis. It’s unbelievable,” he said.

It should be said that Hewitt and Groth are older, and wiser, than Tomic and Kyrgios. But you know that it means everything for them to represent their country.

With Tomic and Kyrgios, even though they say it, you get the feeling they are only doing so because they are supposed to.

If it was down to pure talent, then Tomic and Kyrgios would be the preferred pairing in all of Australia’s Davis Cup matches.

They surely must realise now that it is about plenty more than that. The reminders have been countless.

If social media and talkback radio is anything to go by, the general public are running out of patience with them. Being young and naïve won’t wash forever.

It hasn’t been a great month for Australian tennis, which has dealt with scandal after scandal.

But progression to the semi-finals of the Davis Cup – for the first time since 2006 no less – is a genuinely good story.

If the penny drops with Tomic and Kyrgios, it will be an even better one.