The top-seeded Fish defeated Albert Ramos 6-3, 6-4 and moved closer to what would be his fourth semifinal appearance in his last five tournaments.
Kei Nishikori set up a quarterfinal meeting with Fish by downing Igor Andreev 6-3, 6-3.
Garcia-Lopez will take on Devvarman in the quarterfinals.
The other quarterfinal matches, which were determined Wednesday, will send John Isner against Ivo Karlovic and Ryan Sweeting against Teymuraz Gabashvili.
Fish won this tournament five years ago.
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