Grigor Dimitrov, Milos Raonic and Kei Nishikori. The Bulgarian, the Canadian and Japanese are three players who, at present, can take over from the Fab Five, but still, for one reason or another have failed to win a Grand Slam.
They are at the right age too. Dimitrov is 26, Raonic and Nishikori are 27 and 28 respectively. Everyone is expecting them to take the final leap, which will allow them to compete, and beat in the Slams, the big players of this era, Roger Federer, Rafa Nadal, Novak Djokovic, Andy Murray and Stan Wawrinka.
Whereas the Next Generation is light years away,both from the Fab Five, and from Grigor-Milos-Kei, it seems clear that they are the nearest heirs to Roger, Rafa & Co. Cilic and Tsonga, may be the other variables, while we don't see chances for Tomas Berdych.
Dimitrov seems, among the three, the most in form tennis player. He won his fifth ATP title in Brisbane, against Nishikori, but above all, he played the best Slam of his career, losing to Nadal in the semi-final in Melbourne, in what was the best match of the Australian Open. Dimitrov, than in previous years, seemed to be a different player. He was focused, diligent and aggressive. What does he lack to win a Slam? He needs more mental hold.
Raonic played his first Slam final last year and beat some top players. Generally, he had the best year of his career, despite he won only one tournament. Tactically he improved a lot, also from the mental point of view. His weaknesses are injuries, but above all his backhand that is a burden too great to carry along with his game. Only by improving this key-shot he can make the final leap, but we are confident that within two years he could win a Grand Slam.
Nishikori, after two excellent years, 2014 and 2015, in which he won seven titles and played (and lost) his first Slam final against Cilic, has his secret weapon in his footwork. Physically he suffers from injuries during the seasons, and above all, the Japanese seem to struggle when he plays three sets on five. If he should reach the top and should retain his psycho-physical form during the two weeks of a grand Slam, Kei can beat anyone. There are many variables, but he can do it.
All three players have the opportunity to win a Grand Slam. Although many factors have to occur, only by improving themselves can they takeover from the Fab Five.