Top seed Marty Fish upped his game to see off Gilles Muller and reach the quarter-finals of the Farmers Classic in Los Angeles.
The pair were tightly matched in the the first set, breaking once apiece, but American Fish eased away in the tie-break before racing through the second set to claim a 7-6 (7/1) 6-1 victory.
He will next face Russia's Igor Kunitsyn who needed two tie-breaks to beat another American, Ryan Sweeting, 7-6 (7/4) 7-6 (8/6).
Bulgarian seventh seed Grigor Dimitrov was dumped out in straight sets by Alex Bogomolov Jr, who claimed a 6-4 6-3 win and will next face Thomaz Bellucci, the fourth seeded Brazilian, who beat Colombia's Alejandro Falla 6-0 6-1 in an all-South American encounter.
