Appearing at the Nitto ATP Finals for the fourth time, Marin Cilic is well aware of the challenges ahead of him as he attempts to advance beyond round-robin play for the first time at the elite eight-man event.

The 30-year-old, who began his season by reaching his third Grand Slam final at the Australian Open (l. to Federer), will begin his campaign against German Alexander Zverev on Monday afternoon, with a strong start crucial as he hopes to win his opening match at the tournament for the first time. Joined in Group Guga Kuerten by Novak Djokovic and John Isner, Cilic will be aiming to overcome the disappointment of three-set losses in each of his round-robin matches at The O2 last season.

“Small margins are going to make the difference,” said Cilic. “Playing the top guys is always a big challenge and matches against them are always very close and very tight.”

With a 1-8 record in his previous three appearances, Cilic will be eager to get off to a good start in a city where he has enjoyed success in recent years. Earlier this year, the 18-time tour-level titlist saved one championship point to overcome Novak Djokovic in the Fever-Tree Championships final. Cilic also reached the championship match at Wimbledon in 2017 (l. to Federer).

“This year I feel that I am prepared well and I am feeling good physically as well,” said Cilic. “I feel, mentally, quite fresh and ready for the challenges. I feel these experiences, from previous [appearances], will help me prepare better.”

After early losses in Tokyo, Shanghai and Basel, Cilic rediscovered his best form at the Rolex Paris Masters last week. The 6’6″ right-hander defeated Philipp Kohlschreiber and reigning Nitto ATP Finals champion Grigor Dimitrov, before ending Novak Djokovic’s 30-set winning streak in a three-set loss to the eventual runner-up.

“In Paris, last week, I played great tennis,” said Cilic. “I am feeling good at the moment and [I am] very excited.”

With experience and form, Cilic could finally be set to show his best level at the season finale. But he, as well as the rest of the field, knows it will likely come down to the smallest of margins.

Stefanos Tsitsipas’ rapid rise has been one of the biggest stories on the ATP World Tour in 2018. From beating four opponents inside the Top 10 of the ATP Rankings in Toronto to capturing his first ATP World Tour title in Stockholm and now reaching the Next Gen ATP Finals, the Greek has proven himself capable against the best players in the world.

And one of the main reasons behind the 20-year-old’s success has been his forehand.

“He can go inside-out, inside-in, he hits a really good approach. There’s a lot to build on with his forehand. And I think as he gets stronger, that shot’s only going to get bigger,” said former World No. 4 Brad Gilbert. “His ability when he hits inside-in [is also important] because most guys go inside-out. When he hits it you’re not expecting it and that’s only going to make his inside-out better. So I think the forehand is off the charts.”

An inside-in forehand is when a player goes up the line off that wing from the backhand corner. Many players choose to go inside-out — cross-court to a right-hander’s backhand — since there is more margin of error and they can attack their opponent’s backhand.

“Inside-in, inside-out, it’s all the same. It’s basically what you feel more comfortable with. At the moment, I feel more comfortable with my inside-in. Sometimes I feel playing inside-out a bit more. It’s also from the position of your opponent,” Tsitsipas said. “If you see your opponent is covering his forehand side more, that’s how you decide where you’re going to go.

“But my forehand, as I said, is a big weapon. And, yeah, I choose most of the time inside-in because I just can still play with my forehand. If I go inside-out, [my opponent] probably can find the angle a bit better.”

Tsitsipas’ inside-in forehand, which he says, “has been my biggest weapon”, has featured prominently in some of his biggest victories this year. Gilbert remembers one match in particular: Tsitsipas beat then-reigning champion and World No. 3 Alexander Zverev in Toronto. But it was also the variety he showed off that wing that impressed Gilbert.

“One thing that impressed me was how well on the run he could scramble. He’d hit little squash shots back, flick shots below the net and his ability on big points to play the inside-in or take a forehand and come in is impressive,” Gilbert said. “He’s got a lot of confidence on that shot, which is a great sign for someone his age. Maybe he has the best forehand in the game in a few years.”

For Tsitsipas’ father and coach, Apostolos Tsitsipas, seeing his son’s forehand become a major weapon in the sport is no surprise. That’s the way he structured the first Greek ATP World Tour champion’s game from a young age.

“Because of his one-handed backhand, we definitely developed his game through his forehand,” Apostolos said. “When you’re small like 11, 12, 13, 14, you compete, you’re not strong. So often you build your game from the forehand side. That’s my opinion one of the secrets to build a great forehand from a young age. Usually the two-handers, when they’re playing two-handed from a young age, they don’t really pay so much attention to the forehand. So Stefanos, because he was single-handed, he was always building the point with the forehand, so it was really good for his development. Of course now he is stronger, he can accelerate more and be faster and that helps him and now it’s really a weapon.”

Now the big question is, what makes Tsitsipas’ forehand so strong? Apostolos Tsitsipas compares his son’s forehand grip and motion to that of Juan Martin del Potro’s. And it’s no secret that the Argentine’s forehand is one of the best shots in all of tennis.

“Generally when you have a classic Eastern forehand grip like Stefanos, his motion is closer to Del Potro, his grip is close to Del Potro. Del Potro also has a massive forehand, so it helps him because it’s a much cleaner stroke,” Apostolos said. “You don’t have to think so much how to prepare, you just swing. It’s a natural swing. When you let your arm swing naturally, it creates beautiful mechanics.”

And Tsitsipas will hope those ‘beautiful mechanics’ translate to a beautiful performance on Saturday against Alex de Minaur, in the championship match of the Next Gen ATP Finals in Milan.