Are the Big Four starting to feel the heat coming from the ATP’s crop of Next Gen players?

It sounds like it, based on their glowing assessment of their younger counterparts’ games.

If there’s a consistent assessment between Roger Federer, Andy Murray, Novak Djokovic and Rafael Nadal, it’s that the Next Gen stars are big, powerful and have the game to match.

“I think there is a group of Next Gen players we really need in the game,” says Federer of the ATP’s youth movement. “The ones who are going to carry the game the next ten years.”

“They’re right up there at the top of the rankings. They’re all big, strong guys who hit the ball hard,” says Murray. “[They have] the ability to take the racket out of your hand.”

Even so, there has yet to be a Next Gen star to break through at a Grand Slam. The player to come closest is world No. 4 Dominic Thiem, with a semifinal run at the French Open. Alexander Zverev, just 20, won two ATP Masters 1000 titles this season and is making his debut in London this week.

An unexpected victor emerged from the inaugural Next Gen ATP Finals in Milan with Hyeon Chung going undefeated. The 21-year-old is ranked No. 59, after rising to a career-high ranking of No. 44 in September.