Just two months ago, Rafael Nadal and Daniil Medvedev battled in a five-set epic in the US Open final, with the Russian forging a memorable comeback before the lefty showed his steely resolve to earn a 19th Grand Slam title. Both will need to bring their best to The O2 on Wednesday as they seek to earn their first victory of the 2019 Nitto ATP Finals.

Nadal leads Medvedev 2-0 in their FedEx ATP Head2Head series, with both of their matches coming this year. They are used to high stakes, with their previous battles coming in the final of an ATP Masters 1000 event (Montreal) and a Grand Slam (Flushing Meadows). It will be no different in London, as they try to avoid going 0-2 in Group Andre Agassi play.

Nadal withdrew from his Rolex Paris Masters semi-final less than two weeks ago due to an abdominal strain. But the Spaniard said after his straight-sets loss on Monday against Alexander Zverev that he felt fine, and simply did not play well enough to beat the German.

“It was not a problem with the abdominal at all. I did not feel pain in the abdominal at all. Just Sascha played well and [I] played bad, honestly. We can find reasons or excuses, but at the end of the day, [all that] really matters is I need to play much better,” Nadal said. “I stay positive. I stay competitive, something that [against Zverev] I was not. That’s the thing that I am more disappointed [about], because knowing that I will not be at my 100 per cent in terms of feelings, in terms of movement, in terms of confidence or hitting the ball, I needed my best competitive spirit [against Zverev], and I was not there in that way.”

Nadal will look to turn that around against Medvedev, who in falling to Stefanos Tsitsipas dropped consecutive matches for the first time since June. He will have to raise his level against Nadal, who has lost his first two round-robin matches at the Nitto ATP Finals just once (2009) in eight appearances.

“I’m struggling a little bit with finding back my level I had in the USA and Shanghai and St. Petersburg, which is… I think normal for any sportsman, and that’s what is amazing about the top three, Big Three and Murray before, that even when you kind of look at them and you think, ‘Okay, they are not playing as good as they can’, they still win these matches,” said Medvedev, who recently advanced to the final of six straight tour-level events he played. “That’s what I’m missing right now, and that’s what I’m going to try to work on and still have two matches to come. Hopefully [I] can play them better.”

Medvedev, the fourth seed, has earned eight Top 10 wins this season, making his career’s total nine. As a tournament debutant — two years after competing in the Next Gen ATP Finals in Milan — Medvedev seeks his first victory at the Nitto ATP Finals.

In the evening singles match, defending champion Alexander Zverev and first-time qualifier Stefanos Tsitsipas will meet in the youngest match at this event since a 22-year-old Andy Murray beat a 21-year-old Juan Martin del Potro in 2009 round-robin action.

Zverev entered the tournament 1-5 this season against Top 10 opposition. But with his opening victory against Nadal, the German has now won five of his past six matches at the season finale, all of which have come against Top 10 players.

The 22-year-old’s three most recent victories at The 02 have come against the ‘Big Three’. He is the first player to defeat the legendary trio at this event. In those matches, he did not drop a set, breaking serve nine times.

But Tsitsipas has proven a challenging foe for Zverev, leading their FedEx ATP Head2Head series 3-1, with two of his wins coming this year.

“[They were] both fantastic matches. Especially I think in Beijing it was very, very close and could have gone both ways, even though it was two sets,” Zverev said. “It’s going to be interesting. He played a fantastic match [against Medvedev], I thought, especially for the first time playing here. It’s never easy. I’m looking forward to it.”

Tsitsipas will carry confidence into this matchup after defeating Medvedev for the first time on his sixth attempt. The Greek star let it be known all year he wanted to compete in the season finale. And after an impressive debut on Monday, there are scenarios in which he could qualify for the semi-finals on Wednesday.

Group Andre Agassi Semi-final Qualification Scenarios

“It was actually even better than I dreamt of it,” Tsitsipas said after beating Medvedev. “I felt very relaxed today. I don’t know why. Just the importance of me standing on this court just relaxes me, for some reason. I feel really comfortable, and I felt like I had nothing to be afraid of. Just being on that court is already a big excitement, a big joy. It’s something that I dreamt always, and it does feel very special.”

Raven Klaasen and Michael Venus became the first doubles team to reach the semi-finals at this year’s Nitto ATP Finals, earning their place on Tuesday with a 6-3, 6-4 win against Lukasz Kubot/Marcelo Melo.

”Everything seems to be going great this week. We just keep trying to work hard and persevere together,” Venus said. “We’re just happy to be playing this well at the end of the year and especially in London. It’s such a special event… The atmosphere makes it awesome to play out here.”

The South African-Kiwi pair are 2-0 in Group Jonas Bjorkman after also scoring a straight-sets win on Sunday against Rajeev Ram/Joe Salisbury. They’re making their second team appearance at the season-ending championships and advanced out of round-robin action for the first time. Klaasen also finished runner-up at this event in 2016 with Rajeev Ram (l. to Kontinen/Peers).

”We’re really excited about how we played,” Klaasen said. “Mikey carried me out there today. We’re just happy to be through.”

Read More: Venus & Klaasen: A New Perspective

Klaasen/Venus take a 4-3 lead against Kubot/Melo in their FedEx ATP Head2Head rivalry and have won their past three matches, including victories en route to their two ATP Tour titles this season in Halle and Washington.

Kubot/Melo drop to 1-1 this week, having beaten Ivan Dodig/Filip Polasek on Sunday. Their final round-robin match against Ram/Salisbury will determine the second team to advance out of Group Jonas Bjorkman.

Klaasen/Venus got off to a hot start and broke Kubot early, with Klaasen knocking off a forehand volley for a 3-1 lead in the first set. The South-African Kiwi pair only dropped four points on serve and didn’t offer Kubot/Melo a break point. A comfortable hold from Venus at 5-3 gave his team the early advantage after 32 minutes.

Both teams remained even in the second set until Venus stepped up by hitting the shot of the day at 4-4. With Melo serving on a deciding point, Venus responded to a Kubot smash by flicking a half-volley winner for the break. A big serve by Venus in the next game wrapped up play after 71 minutes.

Michael Venus, that is INCREDIBLE reflexes ?

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

— ATP Tour (@atptour) November 12, 2019

Roger Federer declared that he’s “not allowed to lose anymore” after dropping his opening match to Dominic Thiem at the Nitto ATP Finals. The Swiss stuck to his rule on Tuesday, prevailing 7-6(2), 6-3 against Italian Matteo Berrettini in Group Bjorn Borg.

”It’s unusual to lose and then come back to play again, but I did it last year, so I have some experience,” Federer joked. “I’m very happy with how I played today. Matteo was always going to be difficult with his big serve… I was pretty clean in my own service games and I think that helped today. I hope I can keep it up and maybe even play a bit better in the next match.”

The 38-year-old Federer improved to 2-0 against Berrettini their FedEx ATP Head2Head meeting rivalry, including a straight-sets victory this year at Wimbledon. The Swiss has more match wins (58) and titles (6) than any player in tournament history. Federer, who fell to Dominic Thiem on Sunday, is 17-0 lifetime in his second round-robin match at this event.

”There’s no reason to be too down [after losing to Thiem]. We came here to play three matches and give it all we have. It was the big goal of the season to qualify here, which we did,” Federer said. “I had a day off and there’s plenty of ways to get rid of that loss. Hanging out with my kids will do that for me. I was ready and prepared today. That’s what matters the most right now.”

The match result also impacts Dominic Thiem’s chances at advancing out of round-robin action. He’ll qualify for the semi-finals if he defeats Novak Djokovic in Tuesday’s night session. Thiem is bidding to become the first Austrian semi-finalist at the year-end championships since the event added semi-finals and finals in 1972.

Berrettini, who lost to Djokovic on Sunday, is still looking to become the first Italian to win a match at the season-ending championships.

Next stop: Novak ?@rogerfederer | #NittoATPFinals pic.twitter.com/reLMxtnals

— ATP Tour (@atptour) November 12, 2019

Federer earned the lone break point of the set at 6-5, but Berrettini erased it with a forehand winner. The Swiss drew first blood in the tie-break and earned a 2/1 mini-break advantage after Berrettini overcooked a forehand. Federer raced through the final three points of the set to grab the early lead after 42 minutes. The six-time champion is 21-7 in tie-breaks this season. 

He continued to ride the momentum and broke the Italian to love in the opening game of the second set. Berrettini had a chance to level the match with Federer serving 4-3, but couldn’t convert three break points. A slice forehand from Berrettini found the net in the next game and wrapped up play after 78 minutes.

58 #NittoATPFinals wins for @rogerfederer ?

The six-time champ gets his first victory of the 2019 tournament defeating Berrettini in two sets.

?: @TennisTV pic.twitter.com/Fl5UkmdF9H

— ATP Tour (@atptour) November 12, 2019