KEY BISCAYNE, Fla. (AP) American John Isner upset second-seeded Marin Cilic of Croatia 7-6 (0), 6-3 on Tuesday to reach the Miami Open quarterfinals.
The departure of Cilic, the 2014 U.S. Open champion, leaves fourth-seeded Alexander Zverev of Germany as the highest seed remaining in the draw.
Top-seeded Roger Federer lost his opening match at the tournament, and third-seeded Grigor Dimitrov of Bulgaria lost in the third round.
The 14th-seeded Isner, who reached the Miami Open semifinals in 2015, never faced a break point and made 73 percent of his first serves.
In the quarterfinals, Isner will play 19th-seeded Hyeon Chung, a South Korean who defeated Joao Sousa of Portugal 6-4, 6-3.