ATP Finals 2019 Day 5 Preview: Federer takes on Djokovic in virtual quarterfinal, group winner Thiem takes on eliminated Berrettini

The 50th edition of the ATP Finals at 2019 London sees five-time champion Novak Djokovic clash with six-time champion Roger Federer in a winner-takes-all 'virtual' quarterfinal.

Following his victory over Djokovic in a third set tiebreak, Dominic Thiem has qualified for his first ATP Finals semifinal as the group winner, in the process eliminating Italian Matteo Berrettini from the fray.

On the third and final day of round-robin action in the group, Thiem takes on Berrettini in what has now been reduced to a 'dead rubber'. The day's marquee match-up sees former winners Djokovic and Federer clash for a place in the semifinals.

Berrettini would have only pride to play for against Thiem as the 23-year-old looks to become the first Italian player to win a match at the ATP Finals. Thiem on the other hand would look to become the 30th different player to go 3-0 in round-robin play at the season-ending tournament.

Both Djokovic (8-3) and Federer (13-3) have lost thrice in the third round-robin phase at the ATP Finals. While Federer has only failed once (2008) in negotiating this phase of the ATP Finals , Djokovic has made three group-stage exits (2007, 2009, 2011) at the season-ending tournament.

Let us have a preview of the final day of round-robin action in the group.

Dominic Thiem (x5) vs Matteo Berrettini (x8)

Berrettini (left) and Thiem

Thiem became the first player since Alexander Zverev (2018) to notch up back-to-back wins over Federer and Djokovic at the ATP Finals, defeating the duo in his first two round-robin matches this year.

With the pair of wins, Thiem qualified for the semifinals of the tournament for the very first time, leaving Federer and Djokovic to contest a winner-takes-all virtual quarterfinal shootout.

As round-robin action in the group wraps up on Thursday, Berrettini takes on Thiem with only pride to play for. The Italian would look to go one better than Adriano Panatta (1976) and Corrado Barazutti (1978) and become the first player from his nation to win a match at the ATP Finals.

Thiem leads Berrettini 2-1 in the head-to-head after the pair split their two meetings this season (Vienna semifinal - Thiem, Shanghai quarterfinal - Berrettini).

A win for Berrettini would help him avoid becoming the 51st different player to go 0-3 in round-robin play at the ATP Finals. The last five players to go winless in three round-robin matches at the season-ending tournament are John Isner (2018), Marin Čilić (2017), Tomáš Berdych (2015), David Ferrer (2015) and Richard Gasquet (2013).

Novak Djokovic (x2) vs Roger Federer (x3)

Novak Djokovic and Roger Federer

In the 49th meeting between the pair, and the first since the epic Wimbledon final which saw the Serb win after saving championship points, Djokovic and Federer take on each other with a place in the ATP Finals semifinals at stake.

After trailing in their rivalry for large swathes, Djokovic now leads Federer 26-22 head-to-head. That includes victories in their last five meetings: 2019 Wimbledon final, 2018 Paris Masters semifinal, 2018 Cincinnati final, 2016 Australian Open semifinal and 2015 ATP Finals final.

Djokovic is one of three players, the others being Rafael Nadal and Andy Murray, whom Federer has faced five times at the ATP Finals. The Serb (three), along with Juan Martin Del Potro (two), are the only players to have beaten Federer multiple times at the ATP Finals.

In five matches between the pair at the season-ending tournament, Djokovic leads Federer 3-2. This is the third time Federer and Djokovic are in the same group at the season-ending tournament.

In their two previous group-stage meetings at the tournament, Federer beat the then World No. 1 in 2015 while losing their 2013 clash in three sets. The 2015 ATP Finals round-robin win was also the last time Federer tasted victory against Djokovic in any tournament.

A semifinal place is at stake in Federer and Djokovic's 49th career meeting. Following Thiem's win over Djokovic, the Federer-Djokovic clash has become a winner-takes-all, loser-goes-home match-up.

Federer has never lost more than one group-stage match at the ATP Finals since doing so in 2008. The last time Djokovic lost two-group-stage matches at the ATP Finals was in 2009 when he went 1-2 in group-stage play, while the only other time he did so was on his tournament debut in 2007 when he failed to pick up a round-robin win.

A defeat for Djokovic would end the Serb's chances of clinching a record-tying 6th year-end No. 1 finish.

Both Djokovic (8-3) and Federer (13-3) have lost three times in their final round-robin match at the ATP Finals but haven't done so in six and five subsequent tournament appearances respectively. As the the two players with 36 Grand Slam titles, 62 Masters 1000 titles and 11 ATP Finals titles between them lock horns on Thursday, it remains to be seen which of the two legends lives to fight another day and which one leaves the tournament for an early vacation.