Djokovic seems to be the clear favorite to qualify as the victor from here; I do not expect Cilic, Zverev or Isner to give him too much trouble.
Djokovic is the current favorite to win the event with 8/13 odds while Federer is behind him with 11/4 odds.
The tournament opens on Sunday afternoon when Wimbledon finalist Kevin Anderson takes on French Open runner-up Dominic Thiem, but fans will have to wait until Monday before Djokovic plays his first match.
Djokovic has made an incredible comeback following elbow surgery early in the year, overcoming indifferent form to win Wimbledon and the US Open and haul himself back to the number one spot.
It is hard to judge which was the most surreal image on the eve of the ATP World Tour finals in London:Novak Djokovic scrolling through his mobile phone messages on the Jubilee line or the speaker of the House of Commons, John Bercow, declaring his undying love for Roger Federer in the oil-painted shadow of Betty Boothroyd.
"I would reckon the Novak Djokovic group is the tougher one", Becker said, as quoted on the Express.
Greek tennis star Stefanos Tsitsipas was named on Friday as the most improved player of 2018 by the ATP World Tour Awards. "Five months ago, if you told me that.it was highly improbable at that time, considering my ranking and the way I played and felt on the court". I always have, ever since I qualified for the very first time back in 2002.
Novak Djokovic can now add the "Comeback Player of the Year" award to his vast collection of honours and the Serb can complete his remarkable resurgence by winning a record-equalling sixth title at the ATP Finals next week.
The world No 3 has won four titles this year, including a second consecutive Australian Open, and stands on 99 career singles titles - second only to retired American Jimmy Connors, who amassed 109. Also included are Kevin Anderson and Kei Nishikori.
But Anderson has definitely had better results than Thiem on indoor hardcourts - both this year and in the past. The conditions at the season finale in London are expected to be slightly heavier, but being indoors, with the elements not playing a part, the setting is ideal for Federer's precisely directed weaponry.
The South African has beaten Thiem six times in the eight times they've met this season. In fact, the trio of Cilic, Zverev and Thiem collectively won two matches out of nine at the 2017 Finals and crashed out in the round-robin stage.