Rafa Nadal fears for the future of men's tennis. The world No 3 foresees an era with 300km/h serves, where power dominates above all else.
Nadal, who faces Kevin Anderson in the fourth round of the Australian Open today, also wonders about the impact on the sport's future popularity.
"There is a growing trend in tennis that players are hitting harder ... and thinking less," said Nadal, in a stunning interview in Melbourne. "This is a problem. It's a problem for the players at the top, and if it is a problem for the fan ... I don't know.
"For me personally as a spectator, it is. I don't know what is going to happen in the future [but] I think that the players that are able to use strategy, to construct a point ... they might be part of history."
More than ever before, men's tennis is becoming a power-based game. There is less net play, as courts get faster and racquet technology improves to the point that those who volley are an endangered species.
Serves of up to 220km/h have been common in the past week, with a lot of rallies over in a few shots.
The 14-time grand slam champion Nadal fears this could be the tip of the iceberg.
"[One day], we might have 300km/h serves and then a 300km/h return and [players think] 'if I miss, I'll just go for it on the next point'. It is the way the next generation are thinking and it is logical that is what's coming ... the next generation is this type of player.
"Sure, you have to adapt and nothing is eternal but the truth is since I came on the scene up until now ... the trend is going this way. I don't know if that is what fans and spectators want to see in the coming years."
Nadal could be accused of being a touch hypocritical, as his game has been reliant on bludgeoning rivals into the ground, on hitting the ball with a heavier and harder top spin than anyone else.
The 28-year-old has also embraced the latest racquet technology to generate as much power as possible from his outstanding technique. But his success - like that of Federer and Djokovic - has also been due to many other factors.
There is the outstanding court craft, strategy, mind games, and ability to adapt and out-think opponents across a range of surfaces and conditions.
Could that be slowly disappearing, particularly with the emergence of big-serving giants such as Nick Kyrgios (1.93m), Bernard Tomic (1.96m), Milos Raonic (1.96m), Marin Cilic (1.98m), Kevin Anderson (2.03m) and John Isner (2.08m)?
"It's not about not having talent," said Nadal. "It's about the racquets, the [improved] materials, the speed ... [and] the players are getting taller all the time. Also there are more hard court tournaments and less clay court tournaments ... so the serve and power shots have more value."
Nadal, who has spent 13 years on the ATP tour, struggles to be optimistic about what he sees on the horizon.
"For me as a fan, it doesn't excite me, but I am not anyone special," said Nadal. "I'm just another fan of this sport. It would be good to ask the fans, ask the people, if that is what they want for the future of this sport ... and what they want to keep this sport as big as it is."
Nadal also said he did not expect Roger Federer to exit the tournament so early but that such results were inevitable sometimes.
"It is always a surprise when someone like Federer loses but how many years has he been on top, with hardly any defeats in the most important tournaments? It is logical that it is going to happen, that I'll lose, and Roger. Novak is a bit younger than us but we are all getting older and the career of a tennis player is not eternal.
"I don't know if what has happened will ever happen again, that a few players have made so few errors across the big tournaments over so many years ... it is quite unique."