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 Dimitrov fought back for a memorable 3-6 6-4 3-6 6-4 6-2 win in New York.
Federer was hampered by injury in the latter stages, allowing unseeded Dimitrov to run away with victory.
Dimitrov, 28, will play Russian fifth seed Daniil Medvedev in the last four.
Serena Williams beats Wang Qiang to reach semi-finals
Serena Williams underlined her tag as the favourite for the US Open with a brutal quarter-final win over China’s Wang Qiang in just 44 minutes.
The 37-year-old American broke serve five times and hit 25 winners as she eased to a 6-1 6-0 win over the 18th seed on Arthur Ashe Stadium
Williams, seeded eighth, is chasing a record-equalling 24th Grand Slam title.
She will face Ukraine’s fifth seed Elina Svitolina, who beat Britain’s Johanna Konta, in the semi-finals.
“When I play someone who is playing well I have to step up or go home and I’m not ready to go,” said Williams, who earned her 100th singles win at the US Open.
“I knew I needed to come out tonight and play well. I’m feeling good, had a really tough year and I’m still here.
“Physically I’m feeling great and more importantly I’m having fun every time I come out here.”