The 10th-seeded Czech won 76 per cent of his service points and converted two of his four break point chances to wrap up victory in 84 minutes, avenging the defeat he suffered to Muller in Tokyo last year. The right-hander goes on to face Adrian Mannarino.
Mannarino needed two hours and 38 minutes to get past #NextGenATP star Borna Coric, edging the 20-year-old Croatian 6-4, 2-6, 7-6(3). Mannarino was denied a match point on Coric’s serve in the ninth game of the decider, before being broken as he served for the match at 5-4. But the Frenchman regrouped in the ensuing tie-break to prevail.
Coric had upset eighth seed Dominic Thiem in the third round.
Roberto Bautista Agut set a fourth-round clash with Roger Federer after beating recent Acapulco champion, Sam Querrey, 3-6, 6-2, 6-3 in just under two hours. The 28-year-old Spaniard will look to beat Federer for the first time in six attempts.