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World No. 1 Novak Djokovic has continued to improve his serve in recent years.

The Service Edge: Isner Breaks Down The Turin Contenders

American analyses the service impact of some Nitto ATP Finals qualifiers

Having hit more than 13,000 aces in 15 seasons as a pro, it’s safe to say that John Isner knows a thing or two about serving.

While service performance is often overlooked, when you witness the all-round games of the Top 10 in the FedEx ATP Rankings, Isner believes it may be a key factor at the 2021 Nitto ATP Finals, to be held at the Pala Alpitour in Turin.

Speaking to ATPTour.com, the 6’10” American, who qualified for the season finale in 2018, analyses the service prowess of some performers at the 14-21 November event.

Novak Djokovic (2021 Infosys ATP Stats: 420 aces, 76% first-service points won)
The Serbian superstar, who overcame early service issues in his career, returned to his old motion after he recovered from a right elbow injury in 2017. With the help of Goran Ivanisevic in recent years, Djokovic has made it a consistent weapon. So far in 2021, the World No. 1 has compiled a 48-6 match record and lifted five trophies 

“He's actually someone who's definitely improved his serve as his career has gone on,” says Isner. "He's also someone who got to World No. 1 and is always trying to get better. In the case of the past few years, he's tried to improve his serve. Hiring Goran Ivanisevic is a big part of that. He has improved his serve. We saw at the Australian Open him holding serve with relative ease right throughout that tournament.

“Of course, when you hold serve like that and everything else in your game is the best in the world, you're going to win a lot of matches. His serve has certainly improved. He's probably serving better now than he ever has. He has a lot more confidence to go for big second serves and he's winning a lot more free points on his serve. Not that he really needs to. But he does play a lot of gruelling rallies, so occasionally gets a free point here or there. It definitely helps him out a little bit.”

Daniil Medvedev (599 aces, 78% first-service points won)
Over the past four years under the guidance of coach Gilles Cervara, the Russian has increased his ace count and winning percentage on first serve. This year, the 25-year-old has a 54-12 match record and four titles.

Isner says, "The thing that gets lost with a lot of these guys that are No. 1, 2, 3, 4, 5 in the world is their serves aren't really looked at as their weapons because everything else in their game is so solid. It's kind of like these guys have no weaknesses so people like to focus a lot on Djokovic's speed and Medvedev's speed and their backhands. Rightfully so, but at the same time they serve exceptionally well and the stats back that up also.

“So Medvedev is a tall guy, he goes after a serve. He goes after a lot of big second serves, so he's got a lot of confidence with that shot. I think that's one thing we've seen him improve also over the last few years.”

Stefanos Tsitsipas (475 aces, 76% first-service points won)
After suffering a leg injury in the latter part of the 2020 season, Tsitsipas refined his serve and has compiled 50+ match wins for the second time in three years.

“Lately, this year, from what I've seen, he's serving a lot higher percentage first serve," says Isner. “His serve's a little bit different. He's a guy that his toss gets behind him a little bit. I don't necessarily like that, but he's made it work because he serves incredibly well. I think his first-serve percentage has improved a lot this year.

“I think when I've played him in years past, three, four years ago, it was rarely over 60 per cent. We've seen a lot of times his serve being over 60 per cent and sometimes even 70 per cent first serve. Again, he's another guy who has so much game apart from his serve, that’s it's something you don't really think about. He's another guy who's improved his serve."

Alexander Zverev (688 aces, 77% first-service points won)
The German says, "My serve is the key to my game [and] when it's working, I'm playing great." In 2021, Zverev has collected five tour-level titles and won 28 of his past 31 matches heading into the Nitto ATP Finals.

Isner says, "It's all a confidence thing. A lot of it is very, very mental. In my opinion he's got a very pure motion, but we have seen him double fault a lot in the past and he's taken a lot of heat for that. But right now, he doesn't seem to be doing that at all. I've played him where he's not thinking about his second serve at all. Of course, he's going after his first serve. When he's doing that he's one of the toughest players in the world.

“We saw that in Vienna. He didn't have any matches where he was throwing in 10 or more double faults. If he can keep that at bay he's going to be incredibly tough to beat. His first serve is massive. He's a big guy and he really goes after it. He's got a nice motion. I played him at the Laver Cup and I think he served over 70 per cent. I've seen him play a lot of big matches in the past. He played in a lot of these [ATP] Masters 1000 runs he's been on, he's serving consistently at over 70 per cent first serve and if he does that, there's maybe one or two players that could possibly beat him - Djokovic, maybe Medvedev. When he's confident on his serve, everything else behind it is so solid. He's very tough. He showed that in Vienna."

Andrey Rublev (489 aces, 76% first-service points won)
The Russian, one of the hardest hitters off the ground, broke into the Top 5 for the first time in September and is close to compiling 50 wins in 2021.

"His serve is not one that is as big as those other guys, but he definitely has a good first serve," says Isner. "It's not a weak first serve by any means, but his first serve is one that it could get him on the front foot just a little bit, and that's all he needs because he's one of the best and most aggressive baseliners we have in the world.

"He can hit his spots on his serves, but he's not going to serve 130mph. He might get it 125 [mph], but all he needs is to be on the offence just a little bit. He always seizes that opportunity to go on his front foot and go after the ball, [and] really go after his groundstrokes. It's something over the years that I've seen him do on the practice court. He never, ever relents on a single groundstroke and it's certainly paying off."

Matteo Berrettini (609 aces, 79% first-service points won)
The Italian, one of the biggest servers on the ATP Tour, won two ATP Tour titles and reached the Wimbledon final this season to qualify for the Nitto ATP Finals in Turin.

Isner says, "He's a guy, of all the players who have qualified, where the first thing you talk about is his serve. Berrettini has an incredible first serve, one of the top five first serves in the game, I think. He holds serve with a lot of ease. I wouldn't say his groundstrokes are as good as some of the other players. He makes up for that with that incredible serve.

"We also know how big of a forehand he has on top of that. He really goes after it. He's got a live arm. I like his motion. Just one of those guys. The ball goes up and he just pops it. He's just got this super live arm that some people are blessed with. He's got the ability to hit a serve in the high 130s [mph]. It's a huge weapon."

Two other qualifiers, who will compete at the Nitto ATP Finals for the first time this year, have also impressed. Norway's Casper Ruud has won 74 per cent of his first-service points in 2021 and struck 310 aces, earning him five ATP Tour titles and a 53-15 match record, while Poland's Hubert Hurkacz has fired 553 aces in 56 matches this year.

Editor’s note: ATPTour.com spoke with Isner before Ruud and Hurkacz had qualified for Turin.