Wimbledon is shaping up to be a tournament of upsets.

A day after 15-year-old Cori “Coco” Gauff defeated her tennis idol Venus Williams, unseeded Reilly Opelka knocked off former world-ranked No. 3 Stan Wawrinka on Wednesday. Opelka edged the three-time major major champion 7-5, 3-6, 4-6, 6-4, 8-6 to advance to the third round of a Grand Slam tournament for the first time in his career.

The 6-foot-11 Opelka is a former Junior Wimbledon champion who also made headlines with a first-round upset at the 2019 Australian Open, but this is his first time at the All England Club and only his fourth official major tournament. Ranked No. 63 in men’s singles coming into his match with the No. 22-seeded Wawrinka, Opelka capitalized on his opponent’s four groundstroke errors and earned the only service break of the fifth set in the last game, per ESPN. Perhaps most notably, he eclipsed 140 miles per hour on some of his serves, tying the record for the fastest strikes of the tourney thus far.

Opelka, who was born in Michigan and lives in Florida, is the first American man since 1997 to eliminate a previous Grand Slam champion in his Wimbledon main draw debut, according to ESPN.

Wawrinka has never won a men’s singles tourney at Wimbledon, advancing only to the quarterfinals in both 2014 and 2015. The 34-year-old Swiss star has been a top-20-ranked player this year, however, and peaked at No. 3 in 2014. He has wins at the Australian Open, French Open and US Open under his belt, last claiming a Grand Slam in 2016.