World number two Carlos Alcaraz suffered a shock straight-set defeat by an inspired Tomas Machac in the Shanghai Masters quarter-finals.

Machac, who is ranked 33rd in the world, won a closely fought first-set tie-break before emerging a 7-6 (7-5) 7-5 winner.

Alcaraz put his Czech opponent’s serve under pressure in the first set, but failed to take two break points before losing in a tie-break after just over an hour.

Machac then broke the Spaniard in the third game of the second set but Alcaraz broke back to level at 3-3.

However, a wayward game at 5-5 cost Alcaraz his serve, before Machac kept his composure to serve out for the win.

“I was playing unbelievable,” said Machac. “I knew my level would be great because I’m playing the best [I have] right now.

“I had to play this level, otherwise, it is 6-2 6-3 and you go home. I am happy that I managed to play like this for two sets.”

Machac will face world number one Jannik Sinner in the last four, with the Italian beating Daniil Medvedev 6-1 6-4.

Sinner only lost two points as he raced into a 3-0 lead and went on to win the first set in 25 minutes.

Medvedev looked to be struggling physically – he held his right shoulder after being broken in the sixth game and had treatment on it following the opening set.

He improved and made the match more of a contest, but – from 40-0 up on his serve in the fifth game of the second set – was broken again by Sinner, conceding the game with a double-fault.

Medevev had a medical time-out after the seventh game before Sinner went on to complete a comfortable victory in one hour 24 minutes.

“I’m very happy with how I handled this match,” said Sinner.

“It felt like he had a bit of shoulder pain, he couldn’t hit the forehand as well as he liked to.

“It was a great match, great battle, and let’s see what I can do in the semis.”

Meanwhile, France’s Richard Gasquet has announced he will retire after next year’s French Open.

“I think that it is the best moment for me to do it,” the 38-year-old, who is a two-time Wimbledon semi-finalist, told L’Equipe.

“It is the best tournament to do it. It’s magnificent, we have the chance being French to be able to stop in these kind of incredible places.”