If you desire world domination in tennis, best get an early start as Novak Djokovic, Roger Federer and Rafael Nadal have proved.
So, for the likes of Grigor Dimitrov, Milos Raonic and Bernard Tomic -- often touted as the best of the next generation in men's tennis -- the clock is already ticking.
Nadal was just 19 when he burst onto the scene with a first French Open title in 2005.
Djokovic was 20 when he made his breakthrough at the 2008 Australian Open while Federer had his first of 17 Grand Slam titles wrapped up at Wimbledon in 2003 when he was 21.
Bulgarian tyro Dimitrov, the world number 28, is already 22, has been dubbed 'Baby Fed' because of a similar playing style to the great Swiss and is dating Maria Sharapova.
But Dimitrov has yet to win a singles title and has had made just one final, losing to world number two Andy Murray in Brisbane this year.
But there are signs he could make an impact at the French Open which starts on Sunday.
He pushed Nadal to three sets in the quarter-finals in Monte Carlo this year before achieving his biggest win, a second round triumph over world number one Djokovic in Madrid.
After breaking into the top 100 in January 2011, it wasn't until almost two years later that Dimitrov broke the top 50.
"The huge expectations that weighed on him didn't help," said Patrick Mouratoglou, who was Dimitrov's coach until last summer.
Dimitrov is clear about his gameplan for 2013.
"The objective this year was to remain in good health. If I can do that, then making the top 20 will be in my hands."
Australia's Tomic, just 20 and the world number 59, should be rubbing shoulders with the likes of Dimitrov in the top 30.
Instead, his career often makes the front as well as the back pages with a succession of run-ins with the law often accompanying under-whelming performances on court.
Sections of the Australian media dubbed him 'Tomic the Tank Engine' after his meek, second round capitulation to Andy Roddick at the 2012 US Open.
And his Roland Garros build-up has already been derailed by his father John Tomic facing a criminal trial for allegedly assaulting his son's training partner in Madrid.
Elsewhere, Canada's Raonic at 22 years old, and 16 in the world, has four titles but all on hard courts while Polish wildman Jerzy Jancowicz, also 22 and at 23 in the world, currently lacks the subtlety that a two-week Grand Slam event requires.
"I'm always looking around for these guys. Dimitrov has finally taken a step in the right direction, I think he was certainly top-five material," said American great John McEnroe, who won his first major, the 1979 US Open, at 20.
"It's pretty clear to see when you watch the sport that it appears to be more difficult than ever for a teenager, even someone in their early 20s, to break through the way Becker did, Wilander at the French, Sampras. Nadal may be the last guy as a teenager.
"It does seem because of the physicality of the game, it's difficult to see those 18, 19, 20-year-olds be able to jump and win majors."
It's a tough ask to break the ongoing Grand Slam stranglehold -- of the last 39 majors, 34 have been shared by Federer (17), Nadal (11) and Djokoic (six).
But there is always hope.
Murray was 25 when he won his first -- and so far only -- Grand Slam trophy at the 2012 US Open.