London: Dominic Thiem keeps getting the better of Roger Federer.

Thiem beat Federer 7-5, 7-5 in their opening match at the ATP Finals for his fifth win in seven meetings with the Swiss great — and third straight this year.

“To beat him, everything has to fit together. Today I think (that) was the case again,” Thiem said. “Every time, only playing against him is a big honour. Beating him is even better.”

Thiem broke in the opening game of the match and again for a 6-5 lead in the first set after Federer had levelled at 2-2.

The second set went with serve until Thiem broke at love for another 6-5 lead. Federer, a record six-time champion at the ATP Finals, then missed two break points in the next game before netting a backhand return on Thiem’s second match point.

Thiem also beat Federer at the Madrid Masters and in the Indian Wells final this year, but lost to him in the group stage at last year’s ATP Finals.

For Federer, the loss means there’s no room for another slip-up in his next two round-robin matches, against Novak Djokovic and Matteo Berrettini. He’ll probably have to win both in order to reach the semi-finals.

“It’s a normal tournament from here on forward,” Federer said. “Not allowed to lose anymore for me. That’s how it is every week of the year for the last 20 years, so from that standpoint there is nothing new there.”

Djokovic had a much easier start to the tournament, easing past Berrettini 6-2, 6-1 in their first round-robin match.

Djokovic has a chance to overtake Nadal for the year-end No. 1 ranking with a strong showing in London. He trails the Spaniard by 640 ranking points, with a maximum of 1,500 points up for grabs.