The 26th-ranked Spaniard fought back to win 5-7, 6-4, 6-3 and will play either Daniil Medvedev or Rafael Jodar in the final on Sunday.
Alejandro Davidovich Fokina produced a major upset by defeating top seed Alexander Zverev 5-7 6-4 6-3 to reach the Shanghai Masters final, where he will face either former world number one Daniil Medvedev or fellow Spaniard Rafael Jodar.
The 25th seed fired 36 winners in the two-hour, two-minute contest on Saturday to secure only his second victory over Zverev in eight meetings. His previous win against the German came in the round of 32 at the Canadian Open in 2023.
Davidovich Fokina earned his first break of the match to take the second set, forcing a decider with a stunning backhand passing shot on the run that capped a bruising baseline exchange and brought the crowd to their feet.
Carrying that momentum into the final set, Davidovich Fokina broke Zverev for a 2-0 lead and never relinquished control, booking a place in the second ATP Masters 1000 final of his career after finishing runner-up in Monte Carlo in 2022.
Landing 82 percent of his first serves and repeatedly exposing Zverev on the forehand side, he secured one of the biggest victories of his career.
“I knew that if I stayed there all match, I could get at least one chance and I took it there in the second set,” Davidovich Fokina said.
“Then in the third set, I think I was better physically. The early break in the third set gave me a lot of power.
“I focused on just playing, not mattering about the result but enjoying.”
Zverev said fatigue had caught up with him.
“I think a break is quite necessary now,” the 29-year-old told reporters, saying he would monitor his fitness before a tournament in Vienna that begins October 24.
“I carried a little bit of injury, I carried fatigue into the tournament, and I’m OK to lose to a player like this today,” said Zverev, who had felt his ankle at times in Shanghai.
Davidovich Fokina, who missed the North American hard-court swing in August because of injury, has now won nine consecutive matches in China after lifting his second tour-level title at the ATP 250 event in Chengdu last month.
It was a disappointing end to the week for Zverev, a seven-time ATP Masters 1000 champion whose best result in Shanghai remains his runner-up finish to Medvedev in 2019.
The 29-year-old has otherwise enjoyed a fine season, ending his Grand Slam drought at the French Open before claiming a second major title at the US Open and securing the ATP year-end world number one ranking after Jannik Sinner was sidelined for the remainder of the season with a knee injury.
Fifth-seeded Russian Medvedev was playing 12th-seeded Jodar, 20, in the second semifinal.