The leaders of the new school were Alexander Zverev, Daniil Medvedev and Stefanos Tsitsipas. They were the young up-and-comers determined to take down the order that held an iron grip over the kingdom.
Expectations were rising, so they charged headfirst into a realm dominated by three sporting Gods.
“All I hear these few days is Next Gen, Next Gen,” Novak Djokovic said in 2017, with a touch of humour, but also a sense of defiance.
The stubborn Serb reiterated his stance a few years later, swatting away the idea of the Next Gen with admirable arrogance and cheek.
"We are reinventing the Next Gen. Rafa, myself and Roger. We are the Next Gen," he said.
And how right he was.
Now we are aware that the Next Gen were never able to live up to the hype. They were forced to play second fiddle to a trio that defied Father Time for a lot longer than anyone could have anticipated, maintaining an awe-inspiring level of consistency and quality deep into their 30s.
Nadal was still winning Slams in 2022, while Djokovic lifted three of the four majors in 2023.
They kept their younger rivals at arm's length for the next half-decade, like masterful veteran boxers dancing around enthusiastic but wildly erratic amateurs.
But here comes the awkward part. When Nadal and Federer eventually bid farewell to tennis, and Djokovic's decline began, it wasn't Zverev, Medvedev or Tsitsipas who took over.
The middle children of men's tennis found themselves sandwiched between generations. Before they even realised it, they were all very quickly leapfrogged by their child-prodigy little brothers.
A 19-year-old Carlos Alcaraz won his maiden Grand Slam at the US Open in 2022 - the same number as Medvedev, Zverev and Tsitsipas combined.
The Spanish genius now has five majors to his name, while 24-year-old rival Jannik Sinner has four.
Much like the previous Big Three did, Sinner and Alcaraz have monopolised men's tennis, taking the crown that was meant to belong to the Next Gen. They sit atop the world rankings, sharing the last seven Slams between each other.
But it is one thing to be overtaken by two meteoric prospects who are transcending the sport of tennis as we know it. They are also slowly being surpassed by other young stars.
During the early part of 2025, when Sinner was serving his drug ban, an opportunity arose for the late 20-year-olds to insert themselves into the conversation and prove that their powers aren't waning and they remain forces to be reckoned with.
Instead, it was 23-year-old Jack Draper and 19-year-old Jakub Mensik who reigned supreme at Indian Wells and Miami respectively, firmly establishing the fact that the Next Gen were struggling to even compete with the youngsters who were sitting at a slightly different table to Sinner and Alcaraz.
Just recently in Toronto, Sinner and Alcaraz opted to pull out of the tournament to give themselves a rest, opening the door for the rest of the field.
Enter, 22-year-old Ben Shelton, who, like Draper and Mensik, ended up lifting his maiden Masters 1000 title.
Of all the Next Gen, Medvedev has been by far and away the most successful, winning a single Grand Slam at the US Open while becoming world number one for 16 weeks, as well as winning several other big titles
Yet at just 29 years old, his game has fallen to pieces. He has endured an utterly nightmarish 2025, succumbing in the first rounds of the French Open and Wimbledon while failing to make it past the second at the Australian Open.
He has not won a title since 2023 and is outside of the world's top 10 for the first time since 2018.
Once a Russian wall who was able to go toe to toe with anyone from the back of the court, his shot tolerance has dropped off a cliff, while his serve - which used to be one of his most lethal and important weapons - has declined significantly. Will he continue to suffer as he moves into his 30s due to his physical and grinding style of play?
But the US Open represents Medvedev's most successful tournament. A three-time finalist and the scene of where he clinched his one and only Slam, he will be desperate to recapture some of the form that saw him become one of the world's best.
But while Medvedev may be struggling, it is no comparison to the woes of Tsitsipas.
A two-time Grand Slam finalist, a three-time Masters champion and an ATP Finals winner, the Greek is blessed with a suffocating and superb forehand and graceful movement. Yet in the last two years, his career has been clouded by confusion and complications.
A strange on-off coaching relationship with his father and a brief failed stint under Goran Ivanisevic while plummeting down to 28 in the rankings, from a career-high of number three back in 2021, sums up his demise.
At just 27 years old, he has plenty of time on his side. Yet things are likely to get worse before they get better. Tsitsipas has historically not thrived during this time of the season and has never got past the third round of the US Open. He needs a reset, and perhaps he should already have his eyes on 2026.
And what about tennis' great nearly man? Zverev is arguably the best-ever player to have never got his hands on a Grand Slam, and he seems to have lost his way in 2025.
To be fair to the German, he is a slightly different case. He is third in the world rankings and reached the Australian Open final at the start of the year as well as the Cincinnati semis. However, he got crushed by Sinner in the showpiece event in Melbourne, and his performances on the biggest stages have been pretty disappointing.
Zverev remains a major contender for Slams on paper, but realistically, his game is miles away from Sinner and Alcaraz. But with a major crown the only thing missing from a great CV, where does he stand in this current climate?
His counterpunching and passive style of tennis almost makes it seem like he's settling for being the best of the rest. If he wants to take the next step, he must find a way to be more positive when push comes to shove, which would help him jump the final hurdle.
Being a three-time runner-up at majors, the US Open is a chance for him to break his Slam hoodoo. In 2020, he led by two sets and a break against Dominic Thiem in this final, before capitulating and losing out in horrendous fashion.
He has spent some time working with Nadal's uncle and former high-profile coach Toni Nadal, and perhaps a new voice in the coaching department could bring a change of fortunes.
But there is a real chance that the ship has sailed for all three of these players. Simply put, they are not getting any better, while Sinner and Alcaraz will only improve and develop their already electrifying games.
Perhaps one bright spot for the chasing pack ahead of the US Open is the fact that the final Grand Slam of the year has been the most open of all the majors in recent years.
The last six winners of the title in New York have all been different, and since 2008, there have been 11 different champions.
In comparison, during the same 17-year time frame, there have been five different winners at the French Open, five at the Australian Open and six at Wimbledon.
In part, that is because of Nadal, Federer and Djokovic's expertise at those three slams. But it is additionally down to the fact that the US Open comes at the end of the season when players are more fatigued, while the chaos of New York can often affect players.
So, as unrealistic as it is, a sliver of hope remains. Yet how many more chances will they get as more young guns emerge? 18-year-old Joao Fonseca is lurking and will surely soon be a factor at the very top.
The sun is beginning to set on a generation that looks lost and uncomfortable with where they stand in men's tennis. Time will tell whether their race is truly run, but signs are pointing towards the idea that the 'Next Gen' are fading away and becoming yesterday's men.