LONDON - World number two Nadal ousted defending champion Stefanos Tsitsipas 6-4, 4-6 and 6-2 to reach the semifinals at the ATP Finals here on Thursday.

Nadal edged the Greek in the last group match of last year's season finale but failed to qualify for the semifinals despite of two wins.

But this year the situation was much simpler, the winner between the duo will join World number three Dominic Thiem to reach the last four.

The 20-time grand slam champion Nadal was both aggressive and patient. Although a double fault caused him to lose the second set, he was tough enough to see off a rushing Tsitsipas in the deciding set.

"Most of the time, you get here a little bit tired, but this year is a little bit different," said Nadal, who hasn't claimed the victory of the year-ending tournament after nine attempts. "I am just excited to be in the semifinals and I hope to be ready to try my best."

Tsitsipas, 22, felt disappointed with the third set. "I should have handled it a little bit more clever and patiently, but it didn't happen. My serve was not there when I needed it, and these guys, you just have to be there. I wasn't fully present. I wasn't playing in the moment."

Earlier, Thiem lost to Russian debutant Andrey Rublev 6-2,7-5, but it had no impact on his position as the group winner.

The newly-crowned US Open champion will face the winner between world number one Novak Djokovic and German giant Alexander Zverev.