Rafael Nadal came from behind to beat Pablo Carreno Busta and reach the Paris Masters semi-finals on Friday, handing Argentinian Diego Schwartzman the last ATP Tour Finals place in the process.
The 20-time Grand Slam champion claimed a 4-6, 7-5, 6-1 victory, ending his fellow Spaniard's hopes of qualifying for the season-ending tournament in London.
Nadal will play Alexander Zverev for a place in Sunday's final as he bids to win the trophy for the first time, after the German beat Stan Wawrinka 6-3, 7-6 (7/1).
"The thing that really matters to me, I need to return better," said Nadal.
"My serve is working well, I think, so the rest of the game more or less I am playing better and better.
"I need to return better if I want to have chances to keep going."
Schwartzman had his fate taken out of his own hands earlier on Friday with a quarter-final thrashing by Daniil Medvedev, who will face Milos Raonic in the other semi-final.
Top seed Nadal, playing his first event since winning a record-extending 13th French Open title across Paris at Roland Garros last month, would equal Novak Djokovic's record of 36 Masters titles with success this week.
The 34-year-old's best effort at Bercy Arena was a 2007 final loss to David Nalbandian.
The world number two was in trouble when facing three break points in the opening game of the second set, but he saved them all before forcing a decider in the 12th game with a brilliant forehand winner.
He capped a dominant third-set display by reeling off five successive games.
Fourth seed Zverev reached the semis for the first time by extending his winning streak to 11 matches with a hard-fought success over Wawrinka.
The 23-year-old German broke Wawrinka when the Swiss served for the second set before overpowering his opponent in the tie-break.
"Definitely happy to be in the semis and it'll be an interesting one tomorrow (Saturday)... A lot of people are looking forward to that and I am too," said Zverev, who has a 5-1 losing record against Nadal.
- Schwartzman hammered by Medvedev -
Russian third seed Medvedev raced to a 6-3, 6-1 win over Schwartzman in just 64 minutes to set up a last-four clash with Milos Raonic, who saved two match points to beat in-form Frenchman Ugo Humbert 6-3, 3-6, 7-6 (9/7).
Schwartzman had to wait for Nadal's victory to be able to celebrate securing a first ATP Finals appearance.
World number five Medvedev, whose seven ATP titles have all come on hard courts, broke Schwartzman's serve in the third game and did not let up.
Schwartzman never looked like mounting a comeback, winning just one of 28 points on Medvedev's first serve.
"Milos (Raonic) is one of the biggest servers maybe in the history of the sport," said Medvedev.
"So it's not going to be that easy, but for sure when you play indoor hard courts you need to serve well."
The Tour Finals, being played in London for the last time before moving to Turin, get underway on November 15.
Canadian Raonic hammered 25 aces in a typically strong serving display, but had to battle back from the brink of defeat in a deciding-set tie-break against Humbert.
The 22-year-old Humbert was on an eight-match winning streak after triumphing in his last tournament in Antwerp.
But Raonic saved a match point on his opponent's serve after a remarkable 30-shot rally, before some big serves saw him over the finish line.
The former Wimbledon runner-up, who lost the 2014 Paris Masters final to Novak Djokovic, has been beaten in both of his previous meetings with Medvedev.
"It's going to be a tough one, he's been playing especially well this week," Raonic said. "I've just got to be sharp and take care of my serve."