Rafael Nadal has been eliminated from the ATP finals in Turin after Casper Ruud took the first set off American Taylor Fritz in their round-robin match, which also guaranteed that Carlos Alcaraz would end the year as world No.1.
Spaniard Nadal needed to win the tournament to take the rankings top spot from compatriot Alcaraz, but straight-set losses to Fritz on Sunday and Felix Auger-Aliassime on Tuesday left him needing Ruud to lose in straight sets to keep his hopes alive.
The Norwegian, however, took the first set against Fritz at Pala Alpitour Stadium before running out a 6-3 4-6 7-6 (8-6) winner in two hours 12 minutes to take out the Green Group and progress to the semi-finals for the second successive year.
"Only a couple of points decide a match like this," the world No.4 and nine-time tour-level champion Ruud said.
"Fortunately for me, they went my way at the end ... I am sad for Taylor, but I was so happy to see that last forehand sail long. To book my place in the semi-finals felt great.
"I think my movement has been much better in recent weeks ... You will face tougher moments in periods of your career when you are heavier in the legs, and they aren't working. But here in Turin they are working well."
Alcaraz, 19, who is not competing at the tournament due to injury, will be confirmed as the youngest year-end No.1 since the ATP rankings began in 1973.
With his 6-3 6-4 loss to Canada's Auger-Aliassime, the record 22-times grand slam champion Nadal has now lost four successive ATP Tour matches for the first time since 2009.
"There are a couple of positive things. I was able to play two tournaments in the past three weeks. That's a positive, something that I was not able to do for a while," 35-year-old Nadal, who has played only one tournament since the US Open, said.
"I don't think I forgot how to play tennis, how to be strong enough mentally. I just need to recover all these positive feelings and all this confidence and all this strong mentality that I need to be at the level that I want to be.
"I don't know if I going to reach that level again. But what I don't have any doubt is that I (am) going to die for it."
Auger-Aliassime, now coached by Nadal's uncle and long-time mentor Toni who sat in his box, will face Fritz in his final group match with a chance of making the last four.