After 49 FedEx ATP Head2Head meetings, Novak Djokovic knows what an outstanding performance from Roger Federer looks like.

Although Djokovic voiced displeasure with his play against Federer during Thursday’s defeat at the Nitto ATP Finals, he tipped his hat to the Swiss for producing a stunning performance. The Swiss finished the night with 23 winners to just five unforced errors and didn’t drop serve. Having saved two championship points in their clash at this year’s Wimbledon final, the capacity crowd at The O2 knew that Djokovic was capable of a Houdini act, but Federer was not to be denied.

The five-time champion at this event also expressed admiration for Federer delivering world-class tennis at age 38. Thirteen years after he beat the Serbian in their first FedEx ATP Head2Head meeting at the Rolex Monte-Carlo Masters, he continues to find ways to take Djokovic out of his comfort zone.

“He was the better player in all aspects and absolutely deserved to win,” said Djokovic. “He served great, moved well, returned my serve very well. From his end, I think he did everything right. From my end, I was just playing too neutral. I couldn’t read his serve well. Just a pretty bad match from my side.

“[But] I have the utmost admiration for him and everything he’s doing on the court. What he has achieved over the years and what he’s still showing on the court is phenomenal. He’s a role model, even for me, and one of the toughest opponents I’ve had in my career. Looking at his career and what he’s still doing just inspires you.”

The loss was a double blow for Djokovic. Not only did it end his week at The O2, but it guaranteed that Rafael Nadal will finish as year-end No. 1 in the ATP Rankings. Djokovic was looking to finish as year-end No. 1 for a record-tying sixth time.

But the Serbian said it wasn’t the first, or likely the last, difficult moment in his storied career. After 16 years on the ATP Tour, he has learned to navigate the highs and lows that can occur in professional tennis and expected to bounce back quickly.

Read More: Nadal Clinches Year-End No. 1 Ranking

“I have lost so many matches in my life that I know how to move on. This is no different,” Djokovic said. “I’ve played Roger almost 50 times now. Played Rafael Nadal [54] times. Every loss is painful, but when you play your biggest rivals, that adds a little bit of an extra flavor to the win or the loss.

“At the end of the day, we’re professionals and I have been privileged to play this sport in the highest level for many years. I think that gives me experience on knowing how to accept things, move on and look for another opportunity.”

Although Djokovic gave full credit to Federer for the win, he admitted experiencing right elbow pain in the second set. The Serbian stretched out and rubbed his elbow in between points, but did not believe it was a reoccurrence of the injury that forced him to retire during this year’s US Open. Djokovic said he expects to still represent Serbia next week during the Davis Cup Finals in Madrid.

“I hope it’s nothing that will make me unable me to play [in] Madrid. The pain was pretty sharp,” Djokovic said. “But I could play the rest of the match. If I had something really serious, I think I wouldn’t be able to hold the racquet. So it was probably just an awkward, quick movement that I did. It did not pose any issues later on.”

The 49^th FedEx ATP Head2Head meeting between Novak Djokovic and Roger Federer has begun to a sold-out O2 arena in southeast London. The winner will make the Nitto ATP Finals semi-finals and finish in second place in Group Bjorn Borg, behind Austrian Dominic Thiem, who beat both of them earlier this week.

Djokovic leads their FedEx ATP Head2Head series 26-22 and has won three of their five Nitto ATP Finals matchups. The World No. 2 has also won nine of their past 11 meetings.

Federer last beat Djokovic in group play at the 2015 Nitto ATP Finals. The Swiss is trying to reach the last four in London for the 16^th time in his 17^th visit (all but 2008). Federer is 13-3 in his final group matches.

Djokovic is looking to reach the semi-finals in London for the seventh straight time and ninth overall in his 12^th appearance. He is 8-3 in his final group matches.

Two of the greatest of all time. Only one can qualify.

It’s all on the line for Federer & Djokovic ? #NittoATPFinals pic.twitter.com/B5eJ8Y9a76

— ATP Tour (@atptour) November 14, 2019

Matteo Berrettini may not have advanced out of Group Bjorn Borg, but he made history on Thursday at the Nitto ATP Finals. The Italian defeated Dominic Thiem 7-6(3), 6-3 and became the first Italian to win a singles match at the season-ending championships.

”I’m really proud of myself, but more for my team, my family, my friends. It’s been an unbelievable season,” Berrettini said. “I didn’t expect to be here at the beginning of the season. I hope to come back here next year.”

Berrettini finished with a 1-2 record this week. Thiem had already qualified for the semi-finals after his win on Tuesday against Novak Djokovic.

”I always had great fights against [Thiem]. I was able to stay mentally focussed, especially in the first set,” Berrettini said. “I played a great tie-break, so I’m very happy with my performance.”

Berrettini arrived in London at a career-high No. 8 in the ATP Rankings after starting the season outside of the Top 50. His highlights this year include ATP Tour titles in Budapest (d. Krajinovic) and Stuttgart (d. Auger-Aliassime), a maiden Grand Slam semi-final at the US Open and first ATP Masters 1000 semi-final in Shanghai.

He struck first in the opening set and ripped a forehand passing shot past Thiem for a 5-4 lead, but missed his chance to serve out the set and dumped a routine forehand volley into the net. The 23-year-old regrouped strongly by winning the first four points of the tie-break and pumped his first after an ace on set point.

That is a BEAUTY from Berrettini ?

Watch the #NittoATPFinals on @TennisTV ? pic.twitter.com/rOcJrhpWDT

— ATP Tour (@atptour) November 14, 2019

The Italian maintained his momentum in the second set and broke Thiem with a forehand winner for a 4-2 lead. Three games later, a delicate drop shot from Berrettini wrapped up play after 76 minutes.

?? The first Italian ever to win a singles match at the #NittoATPFinals ??

What a way to end a breakthrough season for Matteo Berrettini!

?: @TennisTV | #NittoATPFinals pic.twitter.com/M4po4wk1M3

— ATP Tour (@atptour) November 14, 2019

Two years ago, Stefanos Tsitsipas was an alternate in the Next Gen ATP Finals field. Last season, the Greek star triumphed in Milan. And after beating defending champion Alexander Zverev in straight sets on Wednesday, Tsitsipas has guaranteed his spot in the semi-finals of the Nitto ATP Finals.

The 21-year-old loves challenges. And although he has already booked a trip to the last four at The O2 in London, Tsitsipas will get a chance to eliminate World No. 1 Rafael Nadal from the competition on Friday. If the Spaniard falls, he will not have a chance to move into the semi-finals.

“I’m going to give it my all. I’m going to try to give my soul, and I think it’s also a very good challenge for me in order to prepare for more difficult matches in the semi-finals and the finals, potentially,” Tsitsipas said. “So this match is going to give me a lot. It’s going to educate me, and I’m going to try to get and absorb as much as I can from that.”

Tsitsipas lost the first seven sets of his FedEx ATP Head2Head rivalry with Nadal, but the Greek earned his first win against the lefty earlier this year in Madrid, triumphing in three sets. Nadal leads their series 4-1.

But the World No. 6 will take plenty of confidence into their matchup. Tsitsipas, in his Nitto ATP Finals debut, is the only player yet to lose a set. He was in devastating for against Zverev, losing only five games and saving the lone break point he faced.

“I believe I had a good performance today, which is very satisfying to know, that [there were] no signs of any nerves [and that I was] feeling pretty good on the court,” Tsitsipas said. “It was a good performance. It’s really good to know that I’ll be playing in the semi-finals, but I’ve got to concentrate, keep going the way I have been doing things the past couple of days.”

Tsitsipas has not shied away from clashes with the best players in the world. With his victory against the German, Tsitsipas is now 7-8 this year against Top 10 opposition.

“I always find an extra motivation, an extra reason to play well against the top guys. I consider Sascha also being of this part of this elite group,” Tsitsipas said. “He has done very well over the years. He has, in a way, inspired me to step it up and be part of the Top 10. So in a way I actually owe him a lot. He plays good tennis. Also playing Rafa, Roger, Novak, Andy — I haven’t played Andy, but I think there is plenty to learn from them.

“You have been watching them on TV. You have always wanted to be part of that. So for you, when you step out on the court… it’s a visual. When you see something that you have been dreaming of, I think there is always a spark, kind of an extra reason to play.”

The Zverev win was not the only big one for Tsitsipas, though. The three-time ATP Tour champion arrived in London having not beaten Daniil Medvedev in five tries. But he defeated the Russian for the first time on Monday to get his week started on a high note.

“It’s very fulfilling and satisfying. It’s a big relief when you go through so much pressure and so much will and trying to put yourself into a nirvanic concentration mode. It’s not as easy as people think it is,” Tsitsipas said. “It’s something that fulfills you when you are able to beat players like this and give your best, give your all. These wins mean more than others, and it’s a good thing to have in your portfolio.”

Tsitsipas wouldn’t mind adding a win against Nadal to his Nitto ATP Finals resume either.