The Serbian, winner of the season-ending event for the last four years and five times in total, lost an opening set tiebreak to Austria's debutante Dominic Thiem 12-10.

He battled back in resounding style, however, romping through the next two sets to seal a 6-7, 6-0, 6-2 victory.

Thiem displayed nerves in the first set but the Serbian could not capitalise before the Austrian wasted a break point opportunity at 5-5.

In the tiebreak, eighth seed Thiem had three set points at 6-3 but then served two double faults in a row to allow Djokovic back in.

A third set point went begging with a backhand into the net and the Serbian then saved a fourth before opening up his own opportunity at 9-8 in front.

An attempt at a lobbed winner went wide, however, and Thiem was finally able to wrap up a set which lasted an hour and 16 minutes with a fine forehand into space.

His joy was short-lived though as Djokovic roared through the second set in a mere 22 minutes, with Thiem winning just ten points.

There was more one way traffic in the third as the 29-year-old ensured a winning start in his group, which is named after Czech legend Ivan Lendl.

Djokovic will equal Roger Federer’s record of six titles if he wins the tournament on the fast hard courts, which only invites the top eight available players in the world rankings.

The 12-time grand slam winner is seeded second for the event after losing his number one position to Britain's Andy Murray earlier this month.

The Scot has taken over as the rankings leader following a superb run of results, earning consecutive victories in Beijing, Shanghai, Vienna and Paris.

However, he could relinquish the position back to Djokovic depending on what transpires in London.

France's sixth seed Gaël Monfils lost to Canada's fourth seed Milos Raonic in the second Ivan Lendl group match today, 6-3, 6-4.

The group named after American John McEnroe will then take centre stage tomorrow, with Murray opening against Croatia's seventh seed Marin Cilic.

Japan's Kei Nishikori, ranked fifth, will then do battle with Switzerland's third seed Stan Wawrinka.