Roger Federer, Rafael Nadal and Novak Djokovic have dominated tennis for the last decade and a half - the trio have won 41 of the last 59 Grand Slams since 2006. French Open tournament director Guy Forget thinks there will be a "big hole" when the Big Three call time on their careers.

The Frenchman feels the younger generation are just not strong enough to beat Federer, Nadal and Djokovic consistently at major tournaments. The likes of Alexander Zverev, Stefanos Tsitsipas and Dominic Thiem have made in roads to break the Big Three stranglehold in the ATP tournaments, but have struggled at the Grand Slams.

"The old ones are just always better. The boys have a lot of talent, they can beat Roger, Rafa and Novak on certain days," Forget said, as quoted on Tennis Head.

"But to do it regularly at the Grand Slams, they are just not strong enough for that. Maybe in six months it will be. Maybe in two years. When the three of them stop, we'll have a hole first. No question. I hope it's not that big."

While Forget admits that the Big Three's boots will be hard to fill, he reminisced about the generations of champions before the emergence of Federer, Nadal and Djokovic.

He spoke about the likes of Bjorn Borg, Jimmy Connors and John McEnroe, who were succeeded by the likes of Ivan Lendl, Boris Becker and Stefan Edberg. He is certain that the Big Three will be preceded by "new and completely different champions."

"When these [Lendl, Becker and Edberg] stopped, Agassi and Sampras came along and gave us a fantastic tennis period. Then there was also a small bear market until a young Swiss came up. Then Nadal came along," Forget said.

"In the past 40 years we have been fortunate to experience various great epochs. Even if it is currently hard to imagine that it will be the same as with Roger, Rafa and Novak: it will always go on and new, completely different champions will come."

Nadal and Djokovic are currently preparing for their quarterfinal encounters at the 2021 French Open. They could come against each other in the semi-finals having been drawn in the same half, which could give one of the younger players a chance to win the tournament at Roland Garros.

Rafael Nadal and Novak Djokovic
Rafael Nadal, Roger Federer and Novak Djokovic are on collision course in the French Open Thomas SAMSON/AFP