Britain's Cameron Norrie described his upset of Carlos Alcaraz as "the biggest win of my career" as he reached the Paris Masters last 16 with a gritty comeback against the world number one.

Norrie, who was beaten in straight sets by the Spaniard in this year's Wimbledon quarter-finals, won 4-6 6-3 6-4 in the second round of the ATP Masters 1,000 event in the French capital.

"This win is so big for me," said Norrie, who missed the Olympic Games in Paris and the US Open last year because of a forearm injury.

"I had lost the first round of the qualifiers here last year. Coming back from my injury, I've been trying to enjoy my tennis in the second half of the year and I was able to do that.

"To get the biggest win of my career, my first win over a world number one, and probably the most confident player in the world right now, I am pleased with the way I did it."

Alcaraz won the first set before Norrie responded strongly in the second by breaking early and maintaining his momentum to set up the decider.

The world number 31 then played an incredible backhand pass to break Alcaraz in the final set and saved two break points on his way to victory.

"I actually went for a walk this morning with my coach and we talked through serving for the match and what I needed to tell myself," said Norrie, who beat Sebastian Baez in straight sets in Monday's first round.

"I was so, so tight serving for the match yesterday against Baez.

"I told myself I deserved to be in this moment, I want to be here, and I felt quite relaxed.

"It was a nice walk, a very important walk."

The Briton will next face the winner of the second-round match between wildcards - and cousins - Valentin Vacherot and Arthur Rinderknech.

Alcaraz, who registered 54 unforced errors on Tuesday, was returning from an ankle injury and playing his first match on the tour since beating Taylor Fritz in the Japan Open final at the end of September.

He now risks losing his number one ranking if rival Jannik Sinner, who will face Belgium's Zizou Bergs in the second, goes on to win the Paris tournament.

"I'm really disappointed about my level," Alcaraz said after the defeat.

"I had all the ideas clear, all the goals clear but even in the first set which I won, I felt I could do a lot more than I actually did.

"I have to give credit to Cam. He played really well, a solid match, and I think that was the key."