Carlos Alcaraz described Jannik Sinner as "a beast" and the world's best player after downing the Italian in Wednesday's remarkable China Open final.

Alcaraz and Sinner battled it out for over three hours in the Beijing showpiece match, with Alcaraz eventually triumphing 6-7 (6-8) 6-4 7-6 (7-3).

The Spaniard took the decisive tie-break with a remarkable run of seven straight points, having lost a tie-break in the opening set to fall behind.

At the age of 21 years and 150 days, Alcaraz is the youngest player to defeat the world number one in an ATP event final after losing the opening set since Juan Martin del Potro (20 years, 356 days), who came back to beat Roger Federer at the US Open in 2009.

Speaking after his sixth career win over the Italian (four defeats), Alcaraz outlined his belief he had overcome the very best in the sport.

"He could have won in two, I could have won in two, he could have won in three. It was a really close match," said Alcaraz. 

"Jannik, once again, he showed that he's the best player in the world, at least for me. 

"The level that he's playing, it's unbelievable. It's a really high quality of tennis. His shots, physically, mentally... he's a beast."

Sinner breezed into a 3-0 lead in the third-set tie-break, only for Alcaraz to show extraordinary resilience to maintain his 100% record against Sinner this year, having previously beaten him at Indian Wells and Roland Garros.

"I never lost hope. Honestly I knew that every tie-break Jannik plays is almost on his side," Alcaraz said of the decider. 

"I thought that in the third set, I'm not going to lie down after two mini-breaks for him. I thought, 'okay, I have to give everything that I have just to try to give myself the opportunity to be close'.

"During the whole week I've been playing great tennis. Probably sometimes the luck went to my side a little bit in the matches."