Five-time champion Roger Federer is out of the US Open after Bulgaria’s Grigor Dimitrov won a late-night thriller to finally beat the Swiss great.
Federer, 38, had won all seven of their previous meetings but unseeded Dimitrov fought back to win 3-6 6-4 3-6 6-4 6-2.
Federer, who needed treatment for a back injury in the latter stages, said: “I felt it the whole time, but I was able to play.”
Dimitrov, 28, faces Russian fifth seed Daniil Medvedev in the last four.
World number 78 Dimitrov’s shock win ensured there will be at least one first-time Grand Slam finalist on Sunday.
Third seed Federer, who lost to Australian John Millman in the last 16 last year, has now been knocked out of the US Open by players ranked outside of the world’s top 50 for the second successive year – after never previously having lost to one at Flushing Meadows.
Federer’s exit leaves long-time rival Rafael Nadal as the strong favourite to lift the trophy, with defending champion Novak Djokovic also out after retiring injured from his last-16 match against Stan Wawrinka on Sunday.
Spanish second seed Nadal, a three-time US Open champion, faces Argentine 20th seed Diego Schwartzman in their quarter-final on Wednesday.
Federer’s loss also ended the possibility of the illustrious pair, rather remarkably, meeting at the US Open for the first time in their enduring rivalry.