Rafael Nadal missed out on a place in the ATP Finals last four as defending champion Alexander Zverev claimed the remaining semi-final spot in London.
Nadal, who beat Stefanos Tsitsipas 6-7 (4-7) 6-4 7-5 in the afternoon session, needed Daniil Medvedev to beat Zverev to secure a place in the last four.
However, Zverev came through 6-4 7-6 (7-4) to eliminate Nadal and set up a meeting with Dominic Thiem.
Tsitsipas will face Roger Federer in the other semi-final on Saturday.
Swiss Federer, who is bidding for a seventh title at the tournament, plays Greek Tsitsipas from 14:00 GMT in a match which is live on BBC Two.
Germany’s Zverev takes on Austrian Thiem from 20:00.
World number one Nadal had knocked Russian fourth seed Medvedev out of the tournament with his hard-fought victory over Tsitsipas.
Ultimately, it was a lifeless performance in his opener against defending champion Zverev on Monday that cost Nadal.
Seventh seed Zverev has had a mixed season but put in a convincing performance against Medvedev to advance to the semi-finals.
The German broke Medvedev in the opening game of the match and capitalised as the Russian’s serve faltered in the closing stages.
After staving off a break point, Medvedev held his nerve to force a tie-break, but a double fault allowed Zverev to serve out the match.
Zverev, who did not face a break point all match, fell to his knees after the final point, and said afterwards he could “still improve” on his performance.
“This arena is where I play my best tennis, we don’t play in this atmosphere anywhere else in the world,” he said.
“I think I’ve played two great matches. Only the best four players left are in the semis.”