Rafael Nadal joined Daniil Medvedev in making a shock early exit from the Paris Masters on Wednesday.
While world number one Carlos Alcaraz overcame Yoshihito Nishioka 6-4 6-4 to progress to the last 16, there was no such luck for compatriot Nadal, whose chances of ending the year at the top of the ATP rankings are over after a defeat to Tommy Paul.
World number two Nadal looked well set to progress after claiming the first set 6-3 in just over 40 minutes, yet American Paul rallied to seal the biggest win of his career 3-6 7-6 (7-4) 6-1.
The 22-time grand slam champion said on Tuesday that he is no longer concerned with competing for the top spot in the world, though he will no doubt be frustrated at bowing out at the first hurdle ahead of the ATP Finals later this month.
Paul became the first player to defeat Nadal prior to the quarter-finals of the tournament when he sent a controlled backhand volley away from the forlorn 36-year-old.
Nadal was not the only big-name exit, with world number three Medvedev also slumping to defeat, going down 6-4 2-6 7-5 to Alex de Minaur.
For Australian De Minaur, it was his first win in 19 attempts against a player ranked in the top five and sets up a third-round clash with Frances Tiafoe, who beat Jack Draper.
"It's a good one to get, for sure," said De Minaur. "It's the end of the year, everyone's a bit tired, but I'm very proud of my performance. I just played very smart.
"I knew it was going to be a chess match out there, both baiting each other to be aggressive, but you also didn't want to be too aggressive at times. It was an absolute battle and I'm very happy I was able to come out on top."
It leaves the path open for Alcaraz to retain his place as the world's best player, and the 19-year-old said after his win: "First round in every tournament is never easy.
"You have to be really focused, you have to try to get a good rhythm, good feeling in the first round. I'm really happy with the performance, the level that I played, and I'm looking forward to getting better in the next round."
Ninth seed Taylor Fritz and 10th seed Hubert Hurkacz lost to Gilles Simon and Holger Rune respectively, their defeats ensuring Felix Auger-Aliassime, who overcame Mikael Ymer, and Andrey Rublev will feature in the ATP Finals.
Auger-Aliassime's victory took three hours and 30 minutes, and marked his 14th win in a row.
"Somehow I found a second wind after saving those break points at 4-1," said the Canadian.
"I played better and better, coming through the court much better, serving better. It was pretty epic. Three hours and 30 minutes on the court, quality rallies. He was making me work all the time. Definitely a win to remember."
Fifth seed Stefanos Tsitsipas was also a winner, seeing off Daniel Evans in straight sets.