London: Tennis fans should intoxicate themselves on the elixir still being served up by the best men's generation to grace the game before the well dries up and mere mortals take over, at least that's what the doom-mongers think.
They say when 17-times grand slam champion Roger Federer, claycourt king Rafael Nadal and Serbian winning-machine Novak Djokovic, not to mention the mercurial Andy Murray, hang up their rackets quality, and interest, will suffer.
However, a hungry bunch of young lions are showing all the signs of keeping the flame burning long after the Fab Four settle down to a quiet life polishing their silverware.
At Indian Wells this year the men's Tour launched its ATP#NextGen campaign to promote rising stars aged 21 and under.
They were not short of names.
Volatile but dazzling 21-year-old Australian Nick Kyrgios, Borna Coric, a Croatian teenager with uncanny similarities to a young Djokovic and Alexander Zverev, a German already being compared to Boris Becker, are already established in the top 50.
Throw teenagers Hyeon Chung (South Korea), Karen Khachanov (Russia) and Quentin Halys (France) into the mix alongside American 18-year-old Taylor Fritz, the youngest player in the top 100, Japan's Yoshihito Nishioka, Britain's Kyle Edmund and Swede Elias Ymer and there appears to be critical mass of youngsters boasting 'future grand slam champion' potential.
Five years ago there were seven players aged 21 and under in the top 150, today that figure has risen to 13.
That said, there are no guarantees, according to American Brad Gilbert, a former top-10 player and coach to the likes of Andre Agassi and Murray.
"To become a great player and world number one and grand slam winner, you already have to be great when you're a teenager," Gilbert told Reuters.
"But I believe that there will be someone in this current group who steps up."
Stepping up to join Federer, Djokovic and Nadal, winners of 17, 14 and 11 grand slam titles since 2003, has been notoriously difficult, not just for rising stars, but everyone else.
Since 2010 Murray and Stanislas Wawrinka have won two apiece and Marin Cilic one while Juan Martin del Potro is the only other active player to have won a major.
"It's been tougher to make really big breakthroughs because the Big Four have sustained their excellence for an insane amount of time," Gilbert said.
Kyrgios, a Wimbledon quarterfinalist two years ago aged 19, is leading the charge having risen to a career-high 19th in the world heading to the French Open. He won his first ATP title this year and made semis in Dubai, Miami and Estoril.
Coric reached his first ATP final in India at the start of the year, while Zverev twice crushed former big hope Grigor Dimitrov and almost beat Nadal at Indian Wells.
Zverev cautions against predicting a decline for the big guns any time soon but says he is part of exciting times.
"There are a lot of stories about me being potential number one, about Kyrgios being a potential number one, about Coric, but what I think that shows is there is a very strong group of teenagers or young guys coming up," he said.
"I think we can all do great."
Federer is regularly asked his opinion of who will be the future stars and likes the look of Zverev, having beaten him in Rome last week.
"He will only get better from here," the Swiss said. "He will compete at the top, top 10 at least, if not then top five. Number one is always a big ask. A lot of things need to align for that: consistency, fitness, mental."
With world number one Djokovic turning 29 this week, a few days after Murray, Nadal 30 and Federer soon to be 35, ATP chief Chris Kermode is eagerly waiting to see how the tyros shape up.
"It's exciting," he said. "I've lived through the Borg-McEnroe era, Becker and Agassi and Sampras, people said things would never be the same again.
"But Kyrgios, Zverev, Chung, Coric, they are coming and the great thing is that they have such global appeal. They are at the cusp and we'll see who makes the jump first."
Young lions to watch this year
The top of the men's game has been set in stone for a decade with first Roger Federer and Rafael Nadal, then joined by Novak Djokovic and Andy Murray dominating the top of the ATP rankings.
There are signs that a new generation are ready to carry the torch when time finally catches up on the Big Four.
Here are the ones to watch as the French Open looms (world ranking in parentheses, age in brackets)
19-Nick Kyrgios - Australia (21)
Kyrgios was threatened with ban last year after making lurid remarks about the Stan Wawrinka's girlfriend but is letting his tennis do the talking this season. Won his first ATP title in Marseille and made semis at Dubai, Miami and Estoril. Pushed Rafael Nadal hard on clay at Italian Open and has reached a career-high ranking. "The key for him is maturity and being consistent week in week out," former top-10 player, leading coach and ESPN summariser Brad Gilbert said. "He has the most talent of any of the under 21s but can he put it all together to sustain what he needs to do?"
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44-Borna Coric - Croatia (19)
Lacks the killer weapons of Kyrgios and Alexander Zverev but makes up for that with a maturity beyond his years. Has struggled to chalk up big results against players in the top 20 but did make finals in Chennai and Marrakesh. "He is the best mover of the younger players, a bit of a copy of Djokovic, but less talent than some of the other young guys," Gilbert said.
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48-Alexander Zverev - Germany (19)
Nearly two metres tall and packing huge weapons with his serve and forehand, Zverev also boasts the kind of fluid movement that similarly tall players struggle with. Appears to thrive on the show courts and outplayed Nadal this year in Indian Wells before missing a match point and succumbing. Germany are looking for a new Boris Becker and Zverev could be their best hope, especially at Wimbledon. Coached by his father and former pro, also Alex. "Clearly he has a big game and nice technique and good attitude," Federer said recently.
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72-Taylor Fritz - U.S. (18)
The youngest member of the top 100. By reaching the Memphis Open final, he became the youngest American man to reach a Tour final since Michael Chang in 1989. He lost to Kei Nishikori. A completely different animal to Chang though, relying on a powerful first serve and a crushing forehand. His country's big hope also seems to have the work ethic to go far. "My philosophy is you work so hard that you want to quit tennis. You get to the point where you are so dead and tired. Then you come back and do it again the next day and do it again and again and again," he told the ATP website recently.
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84-Kyle Edmund - Britain (21)
A member of the British Davis Cup team that won the trophy for the first time in 79 years last November, the 21-year-old has benefited from spending time with compatriot Murray during an intensive training camp in Dubai before the start of 2016. Having picked up tips from Murray on how to improve his game, Edmund battled through qualifying before reaching his first ATP quarterfinal in Doha. "He's made great progress. He's a better athlete than I thought. He's got a huge forehand. He's got huge upside," American great John McEnroe said.