ROGER FEDERER faces an uphill task to qualify for the last four of the ATP Finals after a 7-5, 7-5 defeat to Dominic Thiem in his tournament opener Sunday.

The six-time champion was in action in the evening match after Novak Djokovic had swatted aside debutant Matteo Berrettini in the earlier Group Bjorn Borg contest in London.

Federer and Djokovic, who has won the end-of-season event five times, will meet later in the week in a repeat of this year’s Wimbledon final, with two players advancing from the four-man group.

The Swiss 20-time Grand Slam winner recovered quickly from being broken in the first game of the match but the Austrian fifth seed repeated the dose in the 11th game and took the opening set 7-5.

The Austrian stuttered while serving for the match, forced to save two break points, but he held his nerve to take the set 7-5 and seal victory on his second match point.

Thiem came into the match with a 4-2 winning record against his illustrious opponent, but the result is still a surprise. The only time Federer has failed to progress to the knockout stages was in 2008.

Earlier, Djokovic began his quest for a record-equaling sixth ATP Finals title and sixth year-end number one spot with a 6-2, 6-1 romp against Berrettini.

The Serbian was last week nudged off the top position in the rankings by Rafael Nadal, who is also in the eight-man field in London.

Djokovic must reach the final at The O2 to stand any chance of dislodging Nadal but there are major questions over the Spaniard’s fitness.

If the Serbian does claim the year-end No. 1 spot, he would match the record of Pete Sampras and victory at the end-of-season event would equal Federer’s mark. (SD-Agencies)