Britain's Kyle Edmund beat 14th seed Diego Schwartzman to set up a last-16 match against world number one Novak Djokovic at the Paris Masters.
Edmund, 24, has dropped from a career high of 14th in January to 75th in the world and had lost eight consecutive matches before this tournament.
But he followed up his win on Tuesday against Ricardas Berankis by beating Argentina's Schwartzman 7-5 6-3.
Serb Djokovic beat French 20-year-old Corentin Moutet 7-6 (7-2) 6-4.
Djokovic, 32, a four-time champion here, won his first meeting with Moutet by taking the first set on a tie-break and then gaining an early break in the second.
"I didn't play well at all but I somehow managed to win," Djokovic told Amazon Prime. "[Moutet] is an up-and-coming player, very quick. But I found a way to win and that's what matters."
Schwartzman, who reached the US Open quarter-finals in September, had his serve broken in the final game of the opening set, with a double fault handing the British number three the lead.
Edmund then performed well at the start of the second set and held a 4-1 advantage, before sealing his win over the world number 15.
"It was a really good performance," Edmund said. "I was on another level from yesterday, another gear, and had a lot more control.
"I just had something about me and as the match grew I got more and more confidence and I had a really good match."
On Thursday's match against Djokovic, Edmund added: "We've played four times and it's 3-1 to him. We know how we play and I've got nothing to lose.
"He is expected to win and of course he is a legend of the game - hopefully I can take it to him."
Elsewhere, world number two Rafael Nadal is also in the third round after a 7-5 6-4 triumph over French wildcard Adrian Mannarino.
However, four seeded players were knocked out in round two on Wednesday.
Canada's Denis Shapovalov came from a set down to beat Italian 11th seed Fabio Fognini 3-6 6-3 6-3, while American 15th seed John Isner, who lost to Britain's Andy Murray in the 2016 final, was eliminated, losing 7-6 (7-5) 7-6 (7-4) to Cristian Garin of Chile.
Twelfth seed David Goffin of Belgium was beaten 7-5 6-3 by Bulgaria's Grigor Dimitrov and Spanish ninth seed Roberto Bautista Agut fell to a 7-6 (7-2) 7-6 (7-1) loss to Australia's Alex de Minaur.
Fifth seed Dominic Thiem of Austria beat Canada's Milos Raonic 7-6 (7-5) 5-7 6-4 and Greece's Stefanos Tsitsipas, seeded seventh, overcame American Taylor Fritz 7-6 (7-3) 6-3.
The results meant that German Alexander Zverev, who plays Shapovalov in the third round, has qualified for the ATP Finals at the O2 Arena next month.
Zverev will defend his title in London, having beaten Djokovic in last year's final, and is the seventh player to qualify for the season-ending tournament this year along with Nadal, Djokovic, Roger Federer, Daniil Medvedev, Thiem and Tsitsipas.
Italy's Matteo Berrettini is currently in the eighth and final spot but can still be caught by Gael Monfils, Stan Wawrinka and De Minaur.