Carlos Alcaraz heads to the ATP Finals in Turin on the back of titles in Vienna and Paris. But for John Isner, one of the biggest servers in the history of the game, the world No. 3 still has a clear area to work on.

“He can get better. His serve can still get better. I still think his serve can improve so much,” Isner said on the latest episode of the Nothing Major podcast, as reported by Tennishead.

When you watch him from the back of the court, it is like, ‘How can anyone play this sport better?’”

John Isner

The Djokovic example

Isner pointed to Novak Djokovic as proof that a serve can be transformed during a career. “You saw Novak improve his serve in the middle towards late on in his career, and he just went boom,” the American said.

Alcaraz already at work

Alcaraz has not waited for the advice. Ahead of the Laver Cup in September, he adjusted his service motion, with a lower ball toss and a change in the position of his left foot. Asked about it in a recent press conference, the Spaniard explained that he wanted to copy what he had seen in the greatest servers.

“I have watched the best servers in history. Obviously height matters, how tall you are. But the best servers all have that balance, from the back going forward,” he said. “I wasn’t able to do that before, so I changed the motion a little bit. I tried to have more balance and to make the movement smoother. I would say the toss and the balance are everything on the serve.”

“I have been feeling much better on the serve, and I think in Vienna we could see a great improvement on that shot. I’m just really happy about it.”

Carlos Alcaraz

What the numbers say

The ATP statistics over the past 52 weeks partly back Isner up. Alcaraz ranks 13th on the tour in the ATP’s Serve Rating. He is inside the top 10 for first serves in (7th), second-serve points won (8th) and service games won (6th), but only 39th for first-serve points won and 59th for aces per match, with an average of 4.8.

Those figures cover a full year, most of it before the change. In Paris, Alcaraz beat Alex Michelsen, Taylor Fritz, Casper Ruud and Ben Shelton on his way to the title. The ATP Finals start on Sunday, November 15, with the group draw on Thursday.