Novak Djokovic survived an early setback and a warning for smacking a ball into the crowd before making it look all too easy as the world No.2 opened up his ATP Finals campaign with a three-set win over Austrian Dominic Thiem.
The Serb, who has a chance to reclaim the No.1 ranking at the O2 Arena next weekend, rallied to secure a 6-7 (10-12) 6-0 6-2 win on Sunday at the season-ending event.
Djokovic won nine of 10 games to take control of the match after losing the first set in an epic tiebreaker.
"I had, I think, only one set point," Djokovic said of the tie-breaker.
"He just played a good point. I was in the rally, but he just was going for his shots."
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Thiem had his first three set points at 6-3 in the tiebreaker, but he double-faulted twice and then put a backhand into the net to make it 6-6.
Djokovic had a chance, too, leading 9-8. But he couldn't close it out with Thiem serving, eventually hitting a backhand long. The Austrian finally won it on his seventh set point with a forehand winner, prompting Djokovic to smack a ball into the crowd.
He received a warning for his efforts, and was not impressed by a line of questioning by the media suggesting he could have heftier penalty had he hit someone in the crowd.
"It could have been, yes. It could have snowed in O2 Arena as well, but it didn't.
"It is not an issue for me. It's not the first time I did it."
After that, it was just about all Djokovic. The Serb reeled off six straight games to send it to a third set, and then broke Thiem twice more to close it out.
"Even though I lost the first set, I thought I didn't do too many things wrong," said Djokovic, who saved the only break point he faced.
"It was just the very high quality of his game that prevailed in the first set."
In the late match, fourth-seeded Milos Raonic of Canada beat sixth-seeded Gael Monfils of France 6-3 6-4.
Monfils, who was playing at the ATP finals for the first time, hit a pair of "tweeners" in the match, but it was Raonic that got the breaks - one in each half.
Djokovic lost the No.1 ranking to Andy Murray last week, but he can earn it right back in London.
Either will be No.1 if they win the title, as long as Djokovic wins another round-robin match on the way to the final.
With a victory on Sunday, Djokovic can also join Roger Federer as the only players to win the season-ending tournament six times. Federer is not playing in London, sitting out the rest of the season as he continues to recover from knee surgery.
