STUTTGART, Germany -- German qualifier Dustin Brown upset top-seeded Alexander Zverev 6-4, 6-7 (3), 6-3 Thursday to reach the quarterfinals of the Stuttgart Open.
Brown was playing just his second tour-level match of the year but hit a number of spectacular winners to beat the fifth-ranked Zverev and record his first win against a top-10 opponent since 2017.
The 170th-ranked Brown, who is best known for beating Rafael Nadal at Wimbledon in 2015, next plays Gilles Simon or Felix Auger-Aliassime at the grass-court tournament.
Matteo Berrettini caused another upset earlier Thursday, defeating second-seeded Karen Khachanov 6-4, 6-2.
The Italian next faces American player Denis Kudla, who advanced with a 7-5, 6-7 (3), 7-6 (3) win over Gael Monfils.
The Stuttgart Open made the switch from clay to grass in 2015.