Second seed Casper Ruud suffered a shock three-sets second-round defeat to Japan's Taro Daniel at the Mexican Open in Acapulco on Wednesday.
The 2022 US Open and French Open runner-up had struggled past Guido Andreozzi in the first round and followed up that up with a 7-5 2-6 7-6 (7-5) loss to Daniel.
The Japanese qualifier, ranked 125th in the world, won in just under three hours, winning the final three points of the deciding tie-break after Ruud led 5-4.
Ruud had more winners (38-32) but committed 30 unforced errors compared to Daniel's 12.
Taylor Fritz cruised into the last eight with a 6-4 6-4 win over Canada's Denis Shapovalov, setting up a quarter-final with sixth seed Francis Tiafoe, who eased past Feliciano Lopez 6-2 7-6 (8-6).
Fourth seed Holger Rune was too strong for Nuno Borges 6-0 6-2 inside an hour, while eighth seed Alex De Minaur crushed Jacopo Berrettini in just over an hour 6-1 6-0.
Top seed Lorenzo Musetti was a surprise second-round loser at the Chile Open with Jaume Munar triumphing 6-4 6-4 in one hour and 31 minutes.
Fourth seed Diego Schwartzman also bowed out, going down 6-4 4-6 7-6 (7-2) to local Nicolas Jarry.
Jarry will face Yannick Hanfmann in the quarter-finals, while Munar will take on Thiago Monteiro.