Fish, No. 15 in the world, advanced to the quarterfinals with a 4-6, 6-1, 6-2 victory, with 15 service aces and saves on 6-of-7 break points.
Fish will play Ricardas Berankis of Lithuania, who ousted Frenchman Nicolas Mahut 6-4, 7-5.
Also moving on Tuesday was No. 2 seed Alexander Dolgopolov, who dispatched Flavio Cipolla of Italy 6-1, 6-3 in just 53 minutes.
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