Nick Kyrgios described his display as "not bad for a part-time player" after knocking out 21st seed Ugo Humbert in the first round of Wimbledon.
Frenchman Umbert, 23, has won three ATP Tour events in the past 18 months.
"He is an incredible kid and I knew I was a massive underdog," said 26-year-old Kyrgios.
"Not too bad for a part-time player," added the world number 60, who plays Italy's Gianluca Mager next.
"It was easy to get off the couch as Wimbledon is one of my favourite events and I heard there was going to be a crowd so it was an easy decision to come here."
Kyrgios said he woke in up "so much pain" on Wednesday, after his match with Umbert was suspended at 3-3 in the deciding set late on Tuesday.
But at 7-7 he took the last of three break points and duly served out to seal victory in three hours and 26 minutes.
'Boris recognised me' - Berrettini
Queen's champion Matteo Berrettini continued his fine form on grass by seeing off Argentina's Guido Pella to reach round two.
Italian Berrettini fired 20 aces, produced 47 winners and won the final eight games in a 6-4 3-6 6-4 6-0 win.
Berrettini, 25, is seventh seed at SW19, fresh from victory over Cameron Norrie to win Queen's.
Comparisons have been made in recent days between Berrettini and Boris Becker, who also won Queen's on debut before going on to win Wimbledon in 1985.
"Of course it feels nice to hear my name close to him," said Berrettini. "I think the best part was that I met him as soon as I got here.
"He was walking by and stopped. I was surprised because he knew who I was - he made me feel good.
"He told me like, 'well done, now we have something in common'.
"I said, 'yeah, I wish I have everything in common, like all the titles and stuff. I'll try to get there'."
Berrettini's serve was key in beating Pella as he won 83% of points on his first serve, permitting just one break point.
The world number nine clocked 139mph with his fastest serve of the day and faces Dutch player Botic van de Zandschulp - the world number 139 - in round two.
11th & 12th seeds out, Murray v Shapovalov?
Elsewhere on day three of the Championships, Canada's Denis Shapovalov - seeded 10th - moved into round three when Spanish opponent Pablo Andujar withdrew from their match with a rib injury.
Shapovalov, 22, has never reached round three at Wimbledon before and will now face either Britain's Andy Murray or Germany's Oscar Otte.
Spain's Pablo Carreno Busta arrived at SW19 as 11th seed but has now exited in round one on all six appearances at the tournament after a 7-6 (8-6) 6-4 7-5 defeat by Sam Querrey.
Querrey, 33, gave up nine double faults but fired down 22 aces. The American, who has reached the quarter-finals twice and the semi-finals once since 2016, plays Australia's James Duckworth in round two.
Norway's Casper Ruud - seeded 12th - also exited as Australia's Jordan Thompson bettered a five-set marathon lasting four hours and three minutes.
Thompson will play Japan's Kei Nishikori after the Wimbledon quarter-finalist of 2018 and 2019 won the 100th Grand Slam match of his career by beating Australia's Alexei Popyrin in straight sets.
Frenchman Gael Monfils, 34, is 13th seed for the Championships and edged through round one 4-6 6-2 7-6 4-6 6-4 against Australia's Christopher O'Connell, while Bulgaria's 18th seed Grigor Dimitrov and Canadian 16th seed Felix Auger-Aliassime also reached round two.