Novak Djokovic is on course to become an undefeated champion for a third straight year at the Barclays ATP World Tour Finals. Ivan Lendl, the five-time former titlist, was the last player to clinch three straight season finale crowns (1985-87).

The two-time defending champion, who also lifted the 2008 trophy, defeated fourth seed Kei Nishikori 6-1, 3-6, 6-0 in yesterday’s semi-final.

Djokovic is now unbeaten in his past 31 indoor matches. The three-time year-end No. 1 in the Emirates ATP Rankings has a 61-8 match record on the season, which includes six titles. He dropped just nine games in three round-robin matches prior to his fifth meeting with Nishikori.

Djokovic will face either six-time former winner Roger Federer or third seed Stan Wawrinka in tonight’s final.

The Serbian first broke Nishikori’s serve for a 3-1 lead, when the Japanese star hit a backhand volley wide at 30/40. Djokovic broke a second time at 4-1 and then sealed the 23-minute opener with a hold to 15. He won 18 of 22 points under five strokes.

Djokovic won his seventh straight game, breaking Nishikori to 30 at the start of the second set, but then lost his serve by hitting a double-fault.

Greater weight of shot paid dividends in the eighth game, as Nishikori drew Djokovic to the net before striking a forehand pass for a 5-3 lead.

Nishikori, who beat Andy Murray and alternate David Ferrer in Group B play, dictated with his forehand to level the score at a set apiece.

Nishikori’s momentum, however, ended quickly. Successive groundstroke errors—a forehand and backhand—cost Nishikori on two break-points, from 15/40, in the opening game of the third set. Djokovic held on and then broke down Nishikori’s baseline game to win six straight games for victory in 87 minutes.

Nishikori won four ATP World Tour titles from six finals in 2014, including a runner-up finish at the US Open.  He finishes at a career-best year-end No. 5 in the Emirates ATP Rankings.

On Friday, Djokovic had guaranteed he will finish top of the year-end world rankings for the third time in four years—a fitting reward for another dominant year that saw the Serb win Wimbledon, reach the French Open final and claim five other ATP titles.

The 24-year-old Nishikori, the first Asian player to qualify for the Tour Finals, can leave London with his head held high, but he will be frustrated to have let Djokovic off the hook when he seemed to have turned the tide in his favour in the second set.