Thiem edges Tsitsipas in ATP Finals opener

London's last edition of the ATP Finals opened on Sunday with a repeat of last year's final but this time Dominic Thiem prevailed against Greek defending champion Stefanos Tsitsipas.

Just as in their showdown 12 months ago, the quality was high but the atmosphere was distinctly flat inside an empty O2 Arena as U.S. Open champion Thiem won 7-6 (5), 4-6, 6-3.

Rafael Nadal, bidding to claim the only major title to elude him, starts his challenge later against Russian debutant Andrey Rublev in the day's other London Group match.

"It was a tough match, both of us served well and conditions were fast," Austrian Thiem, playing at the elite year-ender for the fifth time in succession, said on court.

"I know how important it is to have a good start in the first match here."

The ATP Finals, in its 50th edition, is being staged in London's O2 Arena for the 12th and last time before it moves to Turin and sadly plans for a vibrant farewell party in front of the usual sell-out crowds has been scuppered by the COVID-19 pandemic.

The cavernous arena, which holds close to 20,000 people in tournament set-up, was dark and empty as the players walked on court to the usual fanfare and music.

And they provided a high-quality match. There was nothing between them in the first set but Tsitsipas, who saved the only break points on offer, looked set to take the opener when he led 4-1 in the tiebreak, only for Thiem to hit back.

On set point down Tsitsipas had the court at his mercy with an easy put-away but Thiem guessed right to get back into the point with a lob and then forced an error.

Tsitsipas took the second set with an early break but Thiem broke early in the decider and that proved sufficient.