American John Isner upset second seed Marin Cilic 7-6 (7-0) 6-3 to reach the quarter-finals of the Miami Open.
Cilic, Croatia's 2014 US Open champion, was the highest-ranked player left in the draw following Roger Federer's shock loss to world number 175 Thanasi Kokkinakis.
"I am so happy to stay in and I am playing so well this year," said 14th seed Isner, who faces Hyeon Chung next.
South Korea's Chung beat Portugal's Joao Sousa in straight sets.
Isner, 32, who reached the Miami Open semi-finals in 2015, did not face a break point during the match, which lasted one hour 27 minutes.