Britain's Andy Murray returns against Kazakhstan’s Alexander Bublik REUTERSGerman world No 97 Brown came back from a set and a break down to beat Portugal's Joao Sousa 3-6, 7-6 (7/5), 6-4, 6-4.
World No 2 and two-time champion Nadal secured his 850th career victory with a 6-1, 6-3, 6-2 demolition of Australia's John Millman.
Fresh from winning his 10th French Open title, Nadal goes on to face Donald Young for a place in the last 32.
Swiss fifth seed and French Open runner-up Wawrinka was knocked out by Russia's Daniil Medvedev, 6-4, 3-6, 6-4, 6-1.
World No 49 Medvedev, making his Wimbledon debut, handed 33-year-old Wawrinka a sixth first round loss at the All England Club, although his efforts were hampered by a left knee injury which required an ice pack at the changeovers.
Medvedev, 21, kissed the Centre Court grass to celebrate his victory, his first at any Slam.
There was plenty of emotion too for 2011 and 2014 Kvitova as the popular Czech downed Sweden's Johanna Larsson 6-3, 6-4.
Kvitova was playing just her eighth match since suffering a potentially career-ending hand injury fighting off a knife-wielding burglar at her home in December.
Former world number one Azarenka defeated Cici Bellis of the United States 3-6, 6-2, 6-1 in her first Grand Slam since taking time off after last year's French Open to have her first child Leo in December.
The two-time Australian Open champion made the semi-finals at the All England Club in 2011 and 2012.Nick Kyrgios, who beat Nadal at Wimbledon in 2014, will not get another opportunity to repeat that shock. The combustible 20th seeded Australian was 6-3, 6-4 down to France's Pierre-Hugues Herbert when he called it quits after failing to shake off the hip injury which has plagued him in recent weeks. Women's second seed Simona Halep, blasted off court in the French Open final by Jelena Ostapenko, downed New Zealand qualifier Marina Erakovic 6-4, 6-1. Ostapenko, the 2014 Wimbledon junior champion, saw off Aliaksandra Sasnovich of Belarus 6-0, 1-6, 6-3.Aga with her fans ? #Wimbledon pic.twitter.com/xEteF7RSEp
— Aga Radwanska ?? (@ARadwanskaLive) July 3, 2017


