LONDON, Nov. 11 -- Kai Nishikori beat Roger Federer 7-6(4) 6-3 in their opening match in the Leyton Hewett group in the ATP Finals in London on Sunday.

Nishikori took advantage of 34 unforced errors from Federer to claim only his 3rd win in 10 meetings against the Swiss.

The first set saw the games go with serve, with few options for a break to mean it would be decided in a tie break, where Federer produced a series of uncharacteristic errors to leave Nishikori with five set points. Although he was able to defend the first three, Nishikori finally got the vital winner to take the set 7-6(4).

The first set produced no break points, but the second started with Federer breaking Nishikori's serve only for the Japanese player to break him straight back in two games littered with errors.

Nishikori was on the defense in the fifth game, but held and then broke Federer in the sixth to move 4-2 up, before holding his own serve to go to within just one game of the match.

Federer held to make it 5-3, but Nishikori again stood firm to take the match and Federer will have to improve when he plays Dominic Thiem on Tuesday.

Earlier in the day Kevin Anderson hit a total of 13 aces to beat Thiem 6-3, 7-6(10) in one hour and 48 minutes on Sunday.

The South African used his big serve to good effect on the hard surface in London and took advantage of a slow start by his Austrian rival to claim the first set.

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