An inspired Nick Kyrgios stunned Novak Djokovic in the Abierto Mexicano Telcel quarter-finals, while Rafael Nadal reached the last four.
So often unpredictable, Kyrgios was at his best in a surprise 7-6 (11-9) 7-5 win over top seed Djokovic in Acapulco on Thursday.
The Australian served exceptionally well, sending down 25 aces and facing just one break point to advance in one hour, 47 minutes.
It was the first meeting between the pair, and Kyrgios was almost unstoppable on serve.
Kyrgios advanced to a semi-final clash against Sam Querrey, who upset fourth seed Dominic Thiem 6-1 7-5, ending the Austrian's seven-match winning run.
On the other side of the draw, Nadal continued his good record at the ATP 500 event.
The Spanish star and 14-time grand slam champion was below his best but still had enough to get past qualifier Yoshihito Nishioka 7-6 (7-2) 6-3.
A two-time champion at the tournament, Nadal holds a 13-0 win-loss record in Acapulco.
Awaiting him in the last four is Marin Cilic, the Croatian advancing after Steve Johnson withdrew due to an ankle injury.
At the Brasil Open, seeds Pablo Carreno Busta, Pablo Cuevas, Fabio Fognini and Diego Schwartzman reached the quarter-finals.