Reilly Opelka, 21, upsets three-time Grand Slam champion Stan Wawrinka at Wimbledon

The No. 22-seeded Stan Wawrinka lost his second-round match at Wimbledon to a 21-year-old American tennis player Wednesday.

Reilly Opelka, 21, defeated the three-time Grand Slam champion Wawrinka 7-5, 3-6, 4-6, 6-4, 8-6.

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“At first I had a lot of success serving and volleying, so I kept with that,” he said. “And then as he kind of picked up on what I was doing and started reading my serve a little bit, it was more difficult for me to win points at the net. So I had to play, played a lot of tennis on the baseline today.”

Opelka will be making the third-round of a Grand Slam even for the first time in his career. It’s his first time playing at Wimbledon and only his fourth Grand Slam tournament appearance.

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Wawrinka admitted he started slow.

“I had some chance.” he said. “I start a little bit slow. I was a bit hesitating, not really moving well enough. ... At the end he went for it. He went bigger than me and he deserved to win.”

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Opelka faces the 2016 Wimbledon finalist Milos Raonoic next.

The Associated Press contributed to this report.