The world scene of tennis was ruled by three players between 2003 and 2019 and everybody regard Federer, Nadal amd Djokovic is real tennis greats. But since then the tennis world has started to change and the main reasons were that -
* the three greats have started to move out of the scene due to age and persistent injuries and declining performances - the only survivor in reality is Djokovic - who basically played in the four major tournaments - were he won three of the four - but he vanished from the scene in other tournaments and in near to zero; bit even more important
* the game of tennis has changed - as is normal in all sport codes the new generation of younger tennis players coming through are hitting the balls harder and at faster speed than the tennis greats did, Proven statistics showed a difference of circa 15% in speed of serving and 10% iro ordinary ball speeds in hits by the younger players. besides he speed the younger players found it easier to change direction of hits at speed.
The latter is the main reason why the greats are finding it extremely difficult to remain competitive in the present environment. Watching the games yesterday both Nadal and Murray found it very difficult to remain in contention - they did well enough in chasing balls in the earlier part of games - but then gave upin crucial stages o the match when they ran out of steam.
The younger generation - and I include the Russian speaking Medvedev, Sverev, Tsitsipas and Rublev in that category has for the time being threatening to take over the lead in tennis and 2022 is likely to see the real departure from the game by Federer and Nadal and the decline of Djokovic in the rankings.