Tougher tests will come for Federer, but it was an ideal opportunity for him to adjust to the courts at SW19, in an arena which must feel like a second home for the eight-time champion.
The estimated worth of the Uniqlo deal trumps the $10m (£7.6m) he was reportedly making each year with Nike, which still retains rights to the Swiss star's iconic "RF" logo.
Roger Federer's 21-year run with Nike is over.
"I was excited to wear Uniqlo today, I must tell you", Federer said after his victory in straight sets.
Nike's contract with Federer expired on March 1.
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"I'm very happy, I felt good from the start too which was nice and that was not the case past year against him.
Uniqlo will help Mr Federer continue taking tennis to new places, while exploring innovations in a number of areas including technology and design with him".
"I don´t know if I´m relieved, more motivated, but I am happy to get through that", said Williams, whose return to Slam tennis after pregnancy at Roland Garros last month ended in a fourth round injury withdrawal.
Roger Federer is now with UNIQLO, leaving Nike for a massive deal.
Roger Federer cause a stir on the first day of Wimbledon by wearing Uniqlo instead of Nike. The good thing is it's not theirs forever. "It's very exciting also again to see what's out there, who wants to do something with me".
The former world number one missed the 2016 event as she served a doping ban and was injured previous year when she was planning to appear in the qualifying event.
Federer has been with Nike since 1994, well before his career took off, and he built a popular brand, RF, over the years.