Roger Federer is out of the US Open after a five-set quarter-final defeat to Grigor Dimitrov.
The 38-year-old twice led the unseeded Bulgarian before suffering from a mystery injury problem late on the match.
That gave the 74th-ranked player the inspiration he needed to mount a late comeback and produced a career-best performance in the final two sets.
He raced through the final set to clinch a famous 3-6, 6-4, 3-6, 6-4, 6-2 victory in three hours and 12 minutes on court at Arthur Ashe to deny Federer a chance at a first US Open title in 11 years.
Dimitrov, 28, will face Russian fifth seed Daniil Medvedev in the semi-final after he beat Stan Wawrinka in four sets earlier on Tuesday.
On paper, it seemed nothing could stop Federer from setting up a potential final with Rafael Nadal after comprehensive victory over David Goffin in round four.
Sure enough, Dimitrov started poorly and found himself 3-0 down inside six minutes. Another 24 minutes went and Federer was 6-3 up.
Something awoke inside Dimitrov as twice came back from a set down to take it to a deciding set.
Federer required treatment from the trainer in between the fourth and fifth set, suggesting the veteran was nursing a problem.
And sure enough, the 20-time Grand Slam winner's final set was riddled with errors, as much as Dimitrov also found another level in his game.
A third semi-final in his career beckons, while Federer's long wait for another Major to add to his collection goes on.
