The result matches the third-seeded Swiss's best effort in six visits to Miami and sets up a last 16 meeting with Ukraine's Alexander Dolgopolov, who was a 3-6 6-0 7-6 (7-5) winner over Serb Dusan Lajovic.
Canadian 12th seed Milos Raonic blasted his way into the fourth round with 6-1 6-2 win over Spain's Guillermo Garcia-Lopez in 56 minutes.
Raonic, who exited the Miami tournament in the third round with injuries the last two years, has had no fitness concerns this year, firing 10 aces and surrendering just five points on his serve to Garcia-Lopez.


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