Kei Nishikori, who was coming off a title run at Memphis less than two weeks ago, bombed out of the Abierto Mexicano Telcel, losing 6-4, 6-3 to Sam Querrey on Wednesday.
Querrey advances to his third straight ATP Tour quarter-final where he will face American teenager Taylor Fritz.
It is the first time in four tournaments this season that Japan’s Nishikori has not reached at least the quarter-finals.
“It’s always hard when you play against good players, but it wasn’t my day today,” the second seeded Nishikori said.
“There were many things that I should do better, especially my serve.
“I wasn’t aggressive enough to beat Sam today. Also he was hitting really big serves so there weren’t many chances for my return game.”
Nishikori’s ouster means the tournament is without its top two seeds after David Ferrer’s earlier loss to Alexandr Dolgopolov. – Agence France-Presse