For all the sustained brilliance of Roger Federer, Novak Djovokic and Rafa Nadal - and they will be remembered as three of the best four males to play the sport - along with Rod Laver, their ongoing success is partly down to the merits of the chasing pack.
For whatever reason, the much-hyped group of youngsters in their wake have failed to achieve the big breakthrough.
Whether it is mental, physical, technical or tactical, they haven't managed to take down any one of the "big three" when it really matters – in a grand slam final.
There have been some close shaves – Thiem has reached the past two finals at Roland Garros, while Russian Daniil Medvedev pushed Nadal to five sets in the US Open final last year – but not enough.
German Alexander Zverev in action against Stan Wawrinka in the Australian Open quater-final. Photo / Getty Images
The legendary trio have won the past 12 slams between them, despite all being on the other side of 30.
The sport has got more demanding, and the average age of a top 100 player has increased steadily over the last decade.
But someone should have made their mark by now.
Thiem is 26, and has two finals to his name.
In Melbourne Zverev, 22, has pushed into the last four of a major for the first time, with two quarter-final finishes his previous best.
Greek Stefanos Tsitsipas, 21, has one semifinal from 11 major appearances, while 20-year-old Denis Shapovalov (fourth round) and 23-year-old Karen Khachanov (quarter-final) are still waiting for a career-defining success.
Nadal won his first French Open as an 18-year-old, and had appeared in six major finals (winning four) before his 22nd birthday, despite having to duel with Federer at his peak.
As a 20-year-old Djokovic had already lifted the trophy in Melbourne and been in the US final, even with the presence of the Swiss and Spanish greats.
Federer was a relatively late bloomer, but had still won three grand slam titles at the age of 22.
But the best of Generation Z hasn't had the same impact, which makes you wonder what is missing from their makeup. Especially if you consider that the best years of Federer, Nadal and maybe even Djokovic are behind them.
Dominic Thiem of Austria will face Alexander Zverev in the semifinal after shocking Rafael Nadal. Photo / Getty Images
Federer, 38, is the greatest to hold a racquet – and remains a force – but the best years of the Swiss were between 2006 and 2009, when he reached 15 of 16 major finals, winning nine.
Nadal, 33, arguably peaked between 2010 and 2012, at one point only missing one slam final out of nine, including his treble success in 2010.
Djokovic, 32, seems relentless, but he's not quite the winning machine of 2015 and 2016, when he actually seemed unbeatable.
