Match detailsFixture: (1) Novak Djokovic vs (3) Alexander ZverevDate: 20 November 2021Tournament: Nitto ATP Finals 2021Round: SemifinalVenue: Turin, ItalyCategory: Year-ending championshipsSurface: Indoor HardcourtPrize money: $7,250,000Match timing: Not before 9 pm local time, 8 pm GMT, 1.30 am ISTLive telecast: USA - Tennis Channel | UK - Amazon Prime VideoNovak Djokovic vs Alexander Zverev previewNovak Djokovic at the Nitto ATP World Tour Finals - Day SixWorld No. 1 Novak Djokovic will take on Alexander Zverev in the semifinals of the 2021 ATP Finals on Saturday.Djokovic began his campaign in Turin with a straight-sets victory over Casper Ruud. The Serb was tested in the first set, but managed to edge out the Norwegian in a tiebreak before cruising in the second set.Djokovic secured his spot in the last four in Turin after winning his second round-robin match against Andrey Rublev in straight sets. The Serb maintained his perfect record with a 6-2, 6-1 victory over second alternate Cameron Norrie 6-2, 6-1, coming through the group stages without dropping a set.ATP Tour@atptour🏆 2008🏆 2012🏆 2013🏆 2014🏆 2015❓ 2021@DjokerNole #NittoATPFinals02:56 AM · Nov 20, 202181080🏆 2008🏆 2012🏆 2013🏆 2014🏆 2015❓ 2021@DjokerNole #NittoATPFinals https://t.co/ejXHcXQEjYAlexander Zverev at the Nitto ATP World Tour Finals - Day FiveAlexander Zverev had a much more complicated route to the semifinals. The German was given a helping hand by Matteo Berrettini, who was forced to withdraw from their round-robin tie after the first set due to injury.Zverev then suffered his fifth straight defeat at the hands of Daniil Medvedev. Even though the German put up a strong fight in the final two sets, he could not get over the line against the US Open winner.In his final match of the round-robin stage, Zverev crushed Hubert Hurkacz 6-2, 6-4 to finish second in the group and seal a semi-final berth.ATP Tour@atptourSascha to the semis 👏🇩🇪 @AlexZverev defeats Hurkacz 6-2, 6-4 to qualify for the semi-finals in Turin! #NittoATPFinals7:44 PM · Nov 18, 202179493Sascha to the semis 👏🇩🇪 @AlexZverev defeats Hurkacz 6-2, 6-4 to qualify for the semi-finals in Turin! #NittoATPFinals https://t.co/28CdDAkgaTNovak Djokovic vs Alexander Zverev head-to-headNovak Djokovic and Alexander Zverev have faced each other 10 times, with the head-to-head currently standing at 7-3 in the World No. 1's favor. Djokovic won their most recent contest in the US Open semifinal in five sets.Novak Djokovic vs Alexander Zverev predictionNitto ATP World Tour Finals - Day SixThe World No. 1 is undoubtedly the favorite to win this contest, but Zverev has proven he has the ability to defeat the Serb in best-of-three matches.The German is currently the Tour leader in match wins with a win-loss record of 55-14. He has had one of the best seasons of his career so far, winning five ATP titles, including two Masters 1000 tournaments in Madrid and Cincinnati.Zverev will need to produce a monstrous serving performance if he is to take down the Serb on Saturday. The German will have to land a high percentage of first serves and also be proactive from the back of the court. He can't afford to get into prolonged rallies and allow Djokovic to settle into a rhythm.Djokovic, on his part, will look to attack Zverev's second serve, which is prone to crumbling under pressure. He will also look to direct most of the traffic to the German's forehand, which is by far Zverev's weaker wing.Zverev might be able to take a set, but the Serb has looked in ominous form throughout the tournament and should be able to come away with the win.Prediction: Novak Djokovic to win in three sets.