Is this the year when the next generation of men's tennis finally usurps the "Big Four"? It is a question that has been asked often over the past decade. At first glance, it might seem strange to suggest that the Big Four - the injury-ravaged Andy Murray aside - are about to be replaced. After all, the other three members, Roger Federer, Rafael Nadal and Novak Djokovic have hoovered up the past eight Grand Slams between them. The trio will be the top three seeds at the Australian Open, which begins on Monday, and are the bookies' favourites.

And yet there is increasing conviction among some of the tennis cognoscenti that 2019 will be a year of change. "There's certainly something in the air," said Boris Becker. That "something" can broadly be split into two categories: the credible emergence of younger talent and the reduced invincibility of the Big Four.

Starting with the former group, Becker is well placed to assess the strength of the leading youngsters. Becker won Wimbledon twice before his 19th birthday, and believes that in Alexander Zverev, 21, Karen Khachanov, 22, Stefanos Tsitsipas, 20 and Borna Coric, 22 there are young players ready to become Grand Slam champions.

"Zverev looks like the best of the rest. He is catching up, his victory at the ATP Finals, beating Federer and Djokovic back-to-back was huge, but equally Khachanov winning the Paris Masters, Tsitsipas' performances throughout the year, Coric's performances again. They're knocking at the door very loudly, and eventually it will blow open.

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"There's certainly something in the air, that the young guys are going to break through at the Grand Slams - especially this year."

Brad Gilbert, the American former world No 4 and one-time coach of Murray and Andre Agassi, is equally bullish. "I'll be surprised if one of them doesn't make a slam final this year," he said.

Zverev's victory at the ATP Finals, Khachanov using his fearsome power to bully Djokovic in the Paris final and the elegant Tsitsipas beating four top-10 players at the Rogers Cup provided compelling evidence last year of the "something in the air" to which Becker refers. Zverev, in particular, looks primed to mature into a slam champion since hiring Murray's former coach Ivan Lendl last August to help add mental fortitude to his all-round game.

Now the challenge is for the "Next Gen" to prove they can do it at Grand Slams. Britain's Kyle Edmund, 24, and Hyeon Chung, 22, produced runs to the Australian Open semifinals last year, but none of Zverev, Khachanov, Tsitsipas or Coric have come close to getting that far at a major.

And one only needs to look at their near contemporaries, Grigor Dimitrov, Kei Nishikori and Milos Raonic - the "Lost Gen" - to see that rich talent does not a Grand Slam champion make.

Is there anything about the latest group of gifted youngsters that suggests they can be different? "Mentally, they're starting to have similar qualities to Novak," Becker says. "I think Zverev and Tsitsipas, they don't seem to crack under pressure. When you start to smell the roses you want more of it. I think it's a good sign. They enjoy being good tennis players, they enjoy being on the tour. They know who's winning, they follow the matches. They're in the locker room a lot because they both like the environment.

"They are both tall, that seems to be the way now. But they have an overall game, they're not just big hitters. That's important.

"A lot of the young guys in the past have had a good win and then struggled with the pressure. But for these other players, especially Zverev and Tsitsipas, it looks easy. They have time, they don't panic if they lose a round or two, and they don't get too overjoyed when they win either. For them it's a journey."

This brings us to the second part of the "something in the air" theory - the suspicion there might be chinks in the Big Four's armour. As well as Murray's hip problem, fitness concerns are growing over Nadal, who has suffered terribly with injuries over the past year and not played competitively since September's US Open. Federer looks far less vulnerable, but he endured a rough second half of last season and is not considered as unbeatable as he once was.

The main obstacle is Djokovic, who is less a fly in the ointment than a massive hornet. A crumb of comfort for Zverev, Khachanov and Tsitsipas is that they have all beaten Djokovic at Masters level. But doing so at a slam in Melbourne, Paris, London or New York, is what will define them. We will see at the Australian Open how ready these boys are to become men.