Volkswacht Bodensee - World number 2 Alcaraz knocked out of Shanghai Masters by Machac

The Czech will face world number one Jannik Sinner in the semi-finals, after a surprisingly straightforward 6-1, 6-4 victory over an injured Daniil Medvedev earlier.

Machac edged out Alcaraz in a closely fought first-set tiebreak after neither player was able to break their opponent's serve.

The four-time Grand Slam champion, who had said before the match that he was wary of Machac's speed, appeared to be struggling at the beginning of the second set.

The Spaniard looked like he might make a comeback when he broke in the sixth game to level.

However, Machac powered back and broke Alcaraz again in the 11th game to claim the shock victory and progress to the semi-finals.

Alcaraz said he was "a little bit disappointed about today's loss".

"I really wanted to go further, to play against Jannik, but that's tennis I guess. I just have to accept it," he said post-match.

"I felt like I was playing against top five -– his level was so high," Alcaraz said of Machac.

"It was unbelievable, it was crazy for me."

Twenty-three-year-old Machac said he had "no other options" when playing against Alzaraz.

"I have to play this well to beat him," he said after the match.

Sinner, who Alcaraz beat in the China Open final last week, looked strong from the beginning of his match against Medvedev.

In the first set, which lasted only 25 minutes, the Italian broke Medvedev in the second and sixth games to murmurs of surprise from the crowd.

The Russian kept holding his shoulder, which he had said the day before had "some niggles", and received medical attention several times during the match.

"He didn't play at his best," said Sinner, acknowledging the injury.

"But this can happen and I took advantage of that today. I felt like I was playing some good tennis, especially the first set, trying to keep going in the second set. It was a good performance from my side."

This was the fifth time Medvedev and Sinner have met in the latter stages of tournaments this year.

Sinner beat Medvedev in the semi-finals in Miami, the quarter-finals of the US Open, and in the Australian Open final, but the Russian ended the Italian's hopes in the last eight at Wimbledon in an epic five-set battle.

G.Frei--VB