SHANGHAI -- No. 2-ranked Carlos Alcaraz's 12-match winning streak was ended by Tomas Machac 7-6 (5), 7-5 in the Shanghai Masters quarterfinals Thursday.
It was No. 33 Machac's third tour-level quarterfinal, and the Czech player proved more than a match for the four-time major winner as he earned his second win over a top-five opponent this year in two hours.
Machac will play top-ranked Jannik Sinner in the semifinals.
"I knew that the level of my tennis would be great because I am playing the best right now, for sure," Machac said. "I beat Tommy Paul [in my] last match with an unbelievable performance. With these types of players, I have to play this level otherwise it's 6-2, 6-3 [and] you go home. There is no other option."
Alcaraz, who won the China Open in a thriller against Sinner last week, learned of Rafael Nadal's retirement announcement shortly before going on court but said the news about his idol hadn't affected his match.
"It is a really difficult thing, really difficult news for everybody, and even tougher for me," Alcaraz said. "He has been my idol since I start playing tennis. I look up to him. Proudly, thanks to him, I really wanted to become a professional tennis player. Losing him, in a certain way, is going to be difficult for us, so I will try to enjoy as much as I can when he's going to play.
"But we are going to play in Saudi Arabia and then Davis Cup, so I'm going to try to enjoy as much as I can the time with him. But yeah, it is a shame for tennis and for me."
Sinner advanced to his fifth ATP Masters semifinal of the season by sweeping aside fifth-ranked Daniil Medvedev in straight sets.
Sinner started strongly and faced one break point in his 6-1, 6-4 masterclass over his Russian opponent, who needed treatment on his shoulder during the second set.
"Obviously I'm very happy how I handled today and this match," Sinner said. "It felt like he had a bit of shoulder pain and couldn't hit his forehand as well as he wished to. Hopefully he can recover as fast as possible, but from my side it was a great match, a great battle, and let's see what I can do now in the semifinals."
With Thursday's win, the two-time major winner has leveled his head-to-head series against Medvedev at 7-7, but Sinner has won seven of the past eight meetings.