Rafael Nadal has needed almost two and a half hours to fend off Pablo Cuevas before advancing to the quarter-finals of the Paris Masters 6-3 6-7 (5-7) 6-3.
The outsider threw down 11 aces and broke the top-seeded Spaniard twice before slipping to defeat.
Nadal has never won the Bercy event in the city he calls the most important of his career due to a record 10 titles claimed across town at Roland Garros.
His victory over the Argentine-born Uruguayan was the fourth in five meetings and came 24 hours after claiming year-end number one ranking honours on Wednesday for the fourth time in his career and the first since 2013.
At 31, Nadal is the oldest year-end number one since rankings began in 1973.
"The victories help to keep going on court," he said.
"I've been winning a lot in my career but I've periods when I've been injured. I've had periods when I was not winning. I had doubts, of course.
"But for me it's not about believing in yourself, it's belief when you work. You have to believe when you work. Then when you win, you believe in yourself."
Juan Martin del Potro beat Dutchman Robin Haase 7-5 6-4 to move closer to a place in the season-wrap-up ATP Finals.
The 29-year-old Argentine, playing for a fifth consecutive week during which he won a title, reached a final and a semi-final, won his 20th match since the start of the US Open more than two months ago.
He can now overtake provisional eighth-placed Pablo Carreno Busta in the season points race by reaching the semi-finals.
Del Potro is trying to keep it all in perspective.
"I take extra motivation, it's going to be a good battle in the next round trying to qualify for London," he said.
"But if I don't get to London, I have my home and vacations - both ways are great to me but, of course, I would love to reach London once again.
"This could be fantastic moment for me. I didn't expect to get this close to qualify for London. I didn't expect to reach the top 10 position at this time.
"Everything is very amazing after all my (wrist) problems, all my injuries."
London-bound Dominic Thiem, the fifth seed, went down 6-4 6-4 to Spanish veteran Fernando Verdasco.
"I now have time to work on everything that is wrong in my game," the disappointed Austrian said.
John Isner became one of two Americans into the quarters, beating sixth seed Grigor Dimitrov 7-6 (12-10) 5-7 7-6 (7-3). Compatriot Jack Sock efficiently put out Frenchman Lucas Pouille 7-6 (8-6) 6-3.
Retiring Frenchman Julien Benneteau defeated Belgian seventh seed David Goffin 6-3 6-3.
Third seed Marin Cilic, however, was never in danger against Spain's Roberto Bautista Agut as the Croatian advanced with a 7-6 (7-4) 6-2 win.
