Eight-time champion Roger Federer came from a set down to beat South African debutant Lloyd Harris and reach the second round at Wimbledon today.
Harris took the first set to the surprise of those watching on Centre Court at the All England Club, but Federer fought back to triumph 3-6, 6-1, 6-2, 6-2 in one hour and 51 minutes.
The Swiss, bidding for a record-extending ninth men's title, is set to face Great Britain's Jay Clarke in round two.
"I struggled early on," Federer, who dropped a set in the first round at Wimbledon for the first time since 2010, told BBC Sport.
"I felt a bit frozen, my legs weren't going.
"I felt it was heavy out there.
"The ball wasn't going when I was hitting it and he was hitting it big."
Clarke earned the right to face the 20-time Grand Slam champion after defeating the United States' Noah Rubin 4-6, 7-5, 6-4, 6-4.
Third seed Rafael Nadal had a more straight forward first-round win than Federer, overcoming Japanese qualifier Yūichi Sugita 6-3, 6-1, 6-3.
Awaiting the Spaniard in the second round is controversial Australian Nick Kyrgios, who beat fellow countryman Jordan Thompson 7-6, 3-6, 7-6, 0-6, 6-1 in a match that lasted nearly three-and-a-half hours.
Nadal, an 18-time Grand Slam champion and two-time winner at Wimbledon, lost to Kyrgios at the Mexican Open in Acapulco in Febraury, with the former accusing the latter of "lacking respect".
Kyrgios, meanwhile, recently described the world number two as "salty".
Among the most notable casualties from the men's singles draw today was French Open finalist Dominic Thiem, who became the third top-10 men's seed to suffer a first-round exit after losing 7-6, 6-7, 3-6, 0-6 against America's Sam Querrey.
The fifth seed joins sixth seed Alexander Zverev of Germany and seventh seed Stefanos Tsitsipas of Greece in suffering elimination.
In the women’s singles event, world number one Ashleigh Barty of Australia and defending champion Angelique Kerber of Germany eased through to the second round.
French Open champion Barty overcame China’s Zheng Saisai 6-4, 6-2 and is next due to play Belgium’s Alison van Uytvanck.
Kerber beat compatriot Tatjana Maria 6-4, 6-3 to set up a clash with America's Lauren Davis in round two.
Later in the day, seven-time Wimbledon champion Serena Williams moved into the second round with a straight-sets victory over Italy's Giulia Gatto-Monticone.
Williams, vying to match Australian Margaret Court's all-time record of 24 Grand Slam singles titles, prevailed 6-2, 7-5.
Elsewhere in the women's singles first round, ninth seed Sloane Stephens of the US defeated Switzerland’s Timea Bacsinszky 6-2, 6-4, while two-time champion Petra Kvitová of Czech Republic progressed with a 6-4, 6-2 win against Tunisia's Ons Jabeur.
Two former champions crashed out of the tournament, however, with Spain's Garbiñe Muguruza and Russia's Maria Sharapova both falling at the first hurdle.
Muguruza, the 2017 champion, lost 4-6, 4-6 against Brazilian qualifier Beatriz Haddad Maia.
Sharapova retired at 5-0 down in the final set of her match against France's Pauline Parmentier with a wrist injury.
The 2004 champion won the opening set 6-4 before losing a tie-break 7-4 in the second.