World number one and two, Novac Kjokovic and Rafael Nadal reached the ATP Finals last four by beating Alexander Zverev and Stefanos Tsitsipas respectively,
The Serb world number one beat Zverev 6-3 7-6 (7-4) at the O2 Arena in London. Djokovic, seeking a record-equalling sixth title at the end-of-season tournament, was pushed much more in the second set but raised his level at the crucial time in the tie-break.
He will play Dominic Thiem in the last four today.
Meanwhile, the Spanish world number two overcame Greek Tsitsipas 6-4 4-6 6-2 in London. Nadal, 34, had been the more consistent player until losing serve to drop the second set, but fought back to dominate the decider. The 20-time Grand Slam champion will play Russian Daniil Medvedev in the semi-finals at the O2 Arena today.
“I was playing, I think, a great level of tennis for almost two sets,” said Nadal, who hit 32 winners and made just 13 unforced errors. “The score was close, but in terms of feeling I felt that I was playing better than him. Then the situation changed. He won that game and then I was starting to suffer a little bit more with my serve.
“But it’s always a good feeling when you are playing well and you’re playing against the best players of the world. You know you’re going to be in a tough fight. That’s what happened tonight. I was able to find a way to win. Very happy.”