The 170th-ranked Brown, who is best known for beating Rafael Nadal at Wimbledon in 2015, next plays Canada's Felix Auger-Aliassime, who defeated Gilles Simon 7-5, 6-4 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.
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