NOVAK Djokovic's progress in the O2 Arena this week has been so smooth it is as if the Serb has been fitted with castors.

The world No 1 dropped nine games in three matches in the Barclays ATP World Tour finals and there was a feeling yesterday that the relatively slight Kei Nishikori, his semi-final opponent, should not be introduced to the crowd but served on a plate.

This anticipation of a rout rather than a contest was more a nod to the brilliance of Djokovic than a derogatory verdict on the merits of the 24-year-old Japanese player who has had a wonderful season. He is the world No 5, he beat Djokovic to reach the final of the US Open where he lost to Marin Cilic and he has won four ATP titles this year.

However, the Serb, at 27 and with seven Grand Slams behind him, may yet have his glory days in front of him. This statement may seem absurd on the page, but its validity is reinforced every time one sees him pick up a racket.

He was forced yesterday afternoon to progress into the previously uncharted territories of a third set on the banks of the Thames. Nishikori, who came on court with a 2-2 record against Djokovic, appeared to be so much the sacrificial lamb that there was a smell of mint in the air. He lost the first set 1-6 in a brisk 23 minutes and the Wimbledon champion seemed to be on his way to a smooth, successive 31st win indoors.

Then something curious happened. Djokovic who dropped only two points on his serve in the first set started to struggle ever so slightly. Nishikori, quick and with excellent technique, was given just a glimpse of redemption. He took it to break the world No 1 in a brilliant game in which his final, winning rally included a drop shot, a lob and an imperious forehand.

Nishikori then duly served out to win the set. At one set all, a Nishikori stat was circulated. It is this: the Japanese player has the best decisive set record in the Open era. The world No.5 has gone into a decisive set 23 times this season, but lost only twice. He immediately forced two break points in the first game of the third set. Djokovic brushed those off and subsequently raced to win the set without the loss of the game, with Nishikori ending with a double fault on match point.

Djokovic's 6-1, 3-6, 6-0 victory in one hour 27 minutes was thus a confirmation of his status as an invincible, but also another indication that Nishikori has merits that can be translated into further success next year.

The first Asian to qualify for the tour finals now has his sights on a Grand Slam victory. He has targeted the Australian Open in January as the tournament to build on his appearance in the final.

Djokovic, in contrast, plays his last match of the season today against Roger Federer who beat Stanislas Wawrinka 4-6, 7-5, 6-6 (8-6) and he admitted: "Mentally, the truth is that I'm exhausted. But knowing just that tomorrow is the last match of the season, I'm sure that I will find any necessary drop of strength, mental and physical, to give it all on the court."

He was also disturbed yesterday by the crowd reaction at one point, when they cheered him dropping serve. He applauded ironically on court but said: "Some individuals were going over the line throughout the whole match, some provocations that I usually don't react on, but I did. It was my fault."