Top seed Dominic Thiem threw away the lead as he was dumped out of the quarter-finals by Dan Evans at the Sydney International on Thursday, the Briton winning 3-6 6-4 6-1.
For world number 67 Evans it was a maiden victory over top-10 opposition, overcoming the Austrian in two hours and two minutes to set up a last-four clash with Andrey Kuznetsov, who also came from a set down to see off Pablo Carreno Busta.
Two-time defending champion Viktor Troicki progresses thanks to the withdrawal of Philipp Kohlschreiber due to a back injury, with Gilles Muller - 7-6 (7-5) 6-4 winner against Pablo Cuevas - his last-four opponent.
"[Troicki] hasn't lost a match in Sydney in, like, forever," said Muller.
"He beat me in the semis two years ago. I know he's a great player – he's up there for a long time and it's going to be a tough match.
"For me it's the third year in a row for the semi-finals, so I'd also like to get one stage further. I think I'd be more happy with that than ending his winning streak."
At the ASB Classic, Steve Johnson won 85 per cent of his first serve points to get the better of countryman and second seed John Isner 6-3 5-7 7-6 (7-3).
Johnson heads into another all-American clash in the semi-finals, with Jack Sock having bounced back from losing the first-set to eliminate Jeremy Chardy in a 5-7 6-4 6-3 victory.
The other last-four match in Auckland will see Marcos Baghdatis take on Joao Sousa following respective wins against Jiri Vesely and Robin Haase.