Austrian Dominic Thiem has produced a stunning display of attacking tennis to beat Rafa Nadal 7-6(7) 7-6(4) in a high-quality duel at the ATP Finals in London and seize control of their group.
World No.3 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.
Bidding to win the only big title to elude him, Spaniard Nadal 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 serving at 4-5, when he slipped 0-40 behind with a wayward smash, but the 20-time Grand Slam champion dug himself out of a hole, saving three match points.
But US Open champion Thiem was unshakeable and forged his way into a 6-3 lead in the match's second tiebreak.
Nadal clawed one point back, but Thiem finished it off, when his opponent dragged a backhand wide, a rare unforced error.
Thiem had beaten reigning champion Stefanos Tsitsipas of Greece in his opening round-robin match and will qualify for the semi-finals if Tsitsipas beats Andrey Rublev.
World No.2 Nadal's fate will rest on his final group match against Tsitsipas.