Novak Djokovic
Djokovic dropped the opening set but produced the goods to claiming an opening round robin win. Getty Images

Novak Djokovic began attempts to reclaim the world number one by coming from behind to defeat Dominic Thiem at the ATP World Tour Finals at the O2 Arena. The five-time champion trailed by a set to the debutant Thiem, but rallied to complete a 6-7 6-0 6-2 victory in a match lasting in excess of two hours.

The 23-year-old Thiem showed no fear on his first appearance at the season-ending tour finals, taking the opening set after seven set points in the tie-break. Djokovic was given a court violation for hitting a ball towards his own players' box at the end of the set - but that moment worked to inspire a routine victory.

Djokovic squared the match without dropping a game in the second and broke Thiem's resistance again in game three of the decider to put him on course for victory. As Thiem's unforced error count ticket towards the half century mark, Djokovic put the rookie out of misery with a double break to begin his campaign in London in winning fashion.

"Dominic started very well and he definitely deserved the applause," said Djokovic. "He put in a big effort. We played on a high level and he was serving at a high fist serve percentage. The tiebreak was deserved won by him because he was the better player in the bigger moments and after that I managed to regroup and play very well. I definitely didn't want to him to start off well and I knew the first few games were crucial and I managed to get that break in the opening game and I felt very comfortable on the court and made him play an extra shot."

Following premature exits from his last two Masters Series 1000 events Djokovic knew he had no margin for error in pursuit of history as the year-end world number one and a record-equalling sixth title in Greenwich. Thiem had not won a set in his three previous meetings with the Serb, and won just seven games in their one-sided clash at the French Open earlier in the year.

However, the tournament rookie will have been encouraged by the 12-time major champion's struggles since becoming the eighth player to claim a career grand slam at Roland Garros - and those issues were prevalent in the opening set. Djokovic was unable to build any momentum against an aggressive Thiem who saw off a break point in game four as he began to acclimatise to the illustrious surroundings.

Thiem could have claimed a break of his own in game 11 but shanked a forehand amid another engrossing rally. The exchanges between the two players were now as lengthy as they were entertaining meaning a crowd which had appeared subdued at the start were now absorbed by a set which was among the best of the season.

A tiebreak was required to separate the players and it saw Thiem's backhand come to the fore, yet his nerve continued to be undoing. Six times the Austrian passed up the chance to secure the set, before a blistering forehand thundered past Djokovic - who himself had allowed a set point to come and go - gave the rookie the advantage.

Djokovic was noticeably irritated by his shortcomings which had seen 15 errors flow from his forehand and he fired a ball towards the box where Boris Becker and his coaching team were situated - leading to a court violation. The moment worked to inspire the defending champion however he won six games in a row to level the match in just 23 minutes as Thiem wilted under the pressure.

Though Thiem held at the start of the decider his resistance proved futile as Djokovic stormed into a 2-1 lead as he recaptured his steely defence. The early blow ensured there was an air of inevitability about the result and soon Djokovic had a second break which confirmed a valuable 200 ranking points towards his hopes of claiming the year-end number one for a third straight year.