Russia's Karen Khachanov, seeded 27, stunned mercurial Australian Nick Kyrgios 7-5, 4-6, 7-5, 6-7 (3/7), 6-4 to reach his first Grand Slam semifinal at the U.S. Open on Tuesday.
Khachanov fired 30 aces and a total of 63 winners past Wimbledon runner-up Kyrgios in a big-serving contest.
The 26-year-old will face fifth seed Casper Ruud of Norway for a place in Sunday's final.
"I did it, guys. Finally, you are showing me some love," Khachanov told the mostly pro-Kyrgios crowd at Arthur Ashe Stadium.
"It was a crazy match I was expecting it would be like this. I'm ready to run, to fight to play five sets. We played almost four hours and that's the only way to beat Nick."
The Russian said he had "nothing to lose" when he faces French Open runner-up Ruud on Friday.
Kyrgios was feeling his left knee at each changeover in the first set Tuesday and summoned the trainer after dropping the opener complaining "I can't walk."
It was a rapid-fire first set dominated by serve with Khachanov sending down four successive aces to lead 6-5 before pouncing on the only break point to seal the set.
Despite his physical worries, the 27-year-old Kyrgios, who knocked out defending champion Daniil Medvedev in the fourth round, broke for 2-1 on his way to pocketing the second set.
Kyrgios served up a 47-second service game, courtesy of four aces in a row, but wasted two break points in the ninth game of the third set.
He was soon made to pay as the Russian edged ahead two sets to one.
Kyrgios was handed a code violation for unsportsmanlike conduct as he angrily berated himself at the changeover.
That will likely lead to another cash penalty to add to the $18,500 in fines he carried into Tuesday's tie.
Kyrgios broke for a 3-2 lead in the fourth but handed the advantage straight back with a lazy double fault.
Another opportunity went begging in the ninth game.
However, Kyrgios settled and as the clock ticked past midnight, he played an impressive tiebreak to send the quarterfinal into a decider.
Khachanov broke for 1-0 in the final set while Kyrgios failed to convert break points in the second and fourth games.
The Russian went to match point off a net cord and claimed victory off an unreturned serve after three hours and 39 minutes of action.
Kyrgios hit 31 aces in his 75 winners but his unforced error count of 58 was almost double the 31 of Khachanov.
Earlier Tuesday, Ruud defeated Italy's Matteo Berrettini 6-1, 6-4, 7-6 (7/4) to make his second Slam semifinal of 2022.
In the women's singles, Tunisia's Ons Jabeur became the first African woman in history to reach U.S. Open semifinals while France's Caroline Garcia ended the hopes of American teenager Coco Gauff to advance to the last four.
Jabeur, who also claimed a notable first in July as the first woman from Africa to reach the final at Wimbledon, scored a 6-4, 7-6 (7/4) win over Australia's Ajla Tomljanovic.
The 28-year-old will now face Garcia in the semifinals after the in-form 17th seed dispatched the 18-year-old Gauff 6-3, 6-4 in Tuesday's other quarterfinal.
Tomljanovic had landed in the quarterfinals after a run that included a third-round victory over Serena Williams, in what was most likely the 23-time Grand Slam champion's final singles match before retirement.
But the Croatia-born Aussie's battling campaign came to a grinding halt against the dynamic fifth-seeded Jabeur, the Tunisian attacking from the outset and never letting up.
Tomljanovic admitted she had been outfoxed by an opponent she described as "crafty."
"When she's playing well, it's very hard to find where to go," Tomljanovic said. "Just really impressed with her game."
Jabeur will head into her semifinal against Garcia aiming to extend an unbeaten record against the Frenchwoman after wins at the 2019 U.S. Open and 2020 Australian Open.
Garcia reached the first Grand Slam semifinal of her career after an ultimately emphatic win over American hope Gauff.
She arrived in New York fresh from winning the Cincinnati Masters, and Tuesday's win was her 13th straight singles victory.
The 28-year-old said she was flourishing after regaining full fitness. She took a two-month break from tennis leading up to the French Open in June to recover from an ankle problem.
Gauff meanwhile took satisfaction from her first U.S. Open quarterfinal appearance but admitted her campaign was tinged by disappointment.