Switzerland's Stan Wawrinka reacts after losing his first round match against Russia's Daniil Medvedev in the Wimbledon Championships in London, Britain on July 3, 2017. [Photo/Agencies]

LONDON -- Fifth seed Stan Wawrinka suffered a shock defeat to Daniil Medvedev of Russia 6-4, 3-6, 6-4, 6-1 in the opening day's competition of the Wimbledon Championships on Monday.

Fourth seed Rafael Nadal beat the world No 137 John Millmain of Australia in a lopsided 6-1, 6-3, 6-2 match while Andy Murray begun the defence of his title with a 6-1, 6-4, 6-2 win over world No 134 Alexander Bublik.

The 32-year-old Wawrinka, a three-time Grand Slam champion, needed ice on a knee injury between points as he became the biggest name to fall. World number 20 Nick Kyrgios was the other seeded player failing to reach round two, retiring because of a hip injury.

It was Medvedv's first Grand Slam victory on his Wimbledon debut, and he dropped to his knees and kissed the green stuff.

"At 5-1, already I started thinking what I have to do after the match if I win it," the 21-year-old Medvedev said. "And I did it because it's my first Grand Slam win, it's at Wimbledon - my favourite tournament - I had to kiss the grass, I guess. Even though people do it when they win the slam, I did it when I win my first match at a slam."

"I had a really great grass court season," he said. "I knew that Stan had some problems at Queen's, he had only played on match on grass. I knew that I would have the chance if I played good and third and first set, I think I was playing amazing."