Novak and Fabio Fognini missed on a great opportunity to beat doubles specialists Lukasz Kubot (POL) and Marcelo Melo (BRA) and reach finals at the BNP Paribas Open. The Serbian/Italian duo lost a tight contest 6-7 (5), 6-2, 6-10 after one hour and 40 minutes of play
Nole will take on Gael Monfils (2) on Saturday, seeking his first title on grass outside Wimbledon.
Novak maintained his winning start to 2017 season with a hard-fought 4-6, 7-6 (7), 6-3 victory over Fernando Verdasco on Friday.
Sunday's contest between Novak and Andy Murray will be the first occasion in history that the year-end no.1 ranking is on the line at the title-match of the season finale.
Novak beat no.10 seed Gael Monfils 6-3, 6-2 on Saturday in the semi-finals and improved to a 50-4 match record on the season.
With a 6-3, 6-1, 6-4 victory over 13th seed Dominic Thiem, Nole is one match win away from completing a career Grand Slam.
Nole recovered from a set down to beat no.6 seed Kei Nishikori 2-6, 6-4, 7-6 in the semi-finals of the ATP Masters 1000 event in Rome.