Novak earned a semi-final spot following a 6-3, 7-6 (4) win over Alexander Zverev (GER, 6). For a place in the final, the top seed will face third-seeded Austrian Dominic Thiem on Saturday at 15:00 CET.
Top seed and five-time former champion failed in attempt to score his second win in as many matches at the 2020 season finale in London, as he was defeated by no.4 seed Daniil Medvedev 3-6, 3-6 in one hour and 21 minutes at The O2 Arena. Novak will look to book his place in the last four when he meets Alexander Zverev (GER, 6) on Friday.
Novak started his Nitto ATP Finals run with a 6-3, 6-2 win over eighth seed Diego Schwartzman. The world no.1 beat the Argentine season finale debutant in 78 minutes to move to 1-0 in Group Tokyo 1970.
Third seed Roger Federer defeated no.2 seed Novak 6-4, 6-3 to reach the last four at the Nitto ATP Finals. The Serb, who has won the season finale title five times, will finish the year as world no.2.
Novak completed the 2016 season with a 65-9 W/L record and seven titles won, and finished year as no. 2 for the second time in his career.
Novak completed dream season capturing a career-high 11th title of the year and fifth ATP World Tour Finals trophy (b.Federer 6-3, 6-4)
Top seed and defending champion suffered his sixth match loss of a season on Tuesday in his second RR match at the Barclays ATP World Tour Finals.