Austria’s Dominic Thiem produced a scintillating display of attacking tennis to beat Rafa Nadal 7-6(7) 7-6(4) in an entertaining duel at the ATP Finals and seize control of their group on Tuesday.

World number three Thiem saved a couple of set points in the first tiebreak before whipping away a forehand to take an opening set in which there was barely anything between the two.

Spaniard Nadal, bidding to win the only big title to elude him, engineered the first break of the match at 3-3 in the second set only for Thiem to reply in stunning fashion.

Nadal was on the brink of defeat when he slipped 0-40 behind serving at 4-5 after a wayward smash, but the 20-time Grand Slam champion dug himself out of a hole, saving three match points.

U.S. Open champion Thiem was unshakeable, however, and forged his way into a 6-3 lead in the day’s second tiebreak.

Nadal clawed one point back, but Thiem finished it off when his opponent dragged a backhand wide, a rare unforced error.

The win means Thiem is first into the semifinals after he also beat reigning champion Stefanos Tsitsipas of Greece in his opening round-robin match in the London Group.

Tsitsipas, meanwhile, survived a match point as he won 6-1 4-6 7-6 (8-6) against Russia’s Andrey Rublev in Tuesday’s other match of Group London 2020.

Tsitsipas will play Nadal on Thursday with the winner joining Thiem in the semi-finals, while Rublev is eliminated after two defeats from two.

Tsitsipas, 22, looked on course for a routine win over Rublev when he took the opening set in only 19 minutes.

However, the 23-year-old Russian broke late on in the second to take the match into a decider.

Rublev led 6-5 in the final-set tie-break but served a double fault, only his second of the match, as Tsitsipas won three points in a row to set up an effective knockout match against Nadal.

Rublev’s defeat means his match against Thiem on Thursday is a dead rubber.