Dominic Thiem became the first man to move into the last four of the ATP Finals event in London.

The Austrian beat Rafael Nadal 7-6, 7-6 in a high-quality match for his second victory of the season-ending event.

Nadal had two set points in the first-set tie-break but could not convert with Thiem eventually securing the win on his fifth match point.

Thiem's qualification was secured when Stefanos Tsitsipas beat Andrey Rublev.

Defending Champion Tsitsipas survived a match point as he won 6-1 4-6 7-6 in 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.