"It's slightly different," he said. "Nine years ago when I came out the first time, it was the most special thing in the world. It still feels amazing. It was an absolute pleasure playing on Centre Court."
Federer came out wearing a white collared jacket with orange trim, then quickly got down to business. He never faced a break point and broke six times.
Federer has a habit of making things look easy. And so it was in the opening game when, stranded at the net, he reached behind him for a reflex forehand volley that landed in for a winner. In the third set, Federer lifted a perfect backhand lob over the 6-foot-6 Hanescu for a break and a 5-0 lead.
It didn't take long for Wimbledon to produce its first upset.
Puig slugged 38 winners in overwhelming Errani in the first match on Court 18. The 19-year-old Puig, playing her first grass-court tournament as a pro, completely outplayed the Italian veteran with her hard-hitting baseline game.
Puig said she has been building on a recent run of success, including a third-round showing at the French Open.
"Definitely pulling off some big career wins and not being afraid to close out matches, which was my problem at the beginning of the year," she said. "Finally just having the confidence to close them out."
Errani was runner-up at last year's French Open and had reached at least the semifinals of three of the last five Grand Slams. But on the slick grass at the All England club Monday, she had only 13 winners and was broken four times.
Puig squandered five match points before hitting a forehand winner past Errani to close the match. The Puerto Rican dropped her racket to the turf and covered her face in her hands.
Errani withdrew from last week's grass-court warmup at Eastbourne with a leg injury, but showed no signs of any physical problems during the match. Asked what went wrong, Errani said "a mix of everything."
"Always tough for me to play here on grass and she played very good," Errani said. "She served very good, did not make many mistakes and hit the ball strong. My big problem here is that I can't move how I want."
It's the third time a top-5 women's seeded player has lost in the first round at Wimbledon since 2001. The others were Martina Hingis in 2000 and Francesca Schiavone in 2010.
Monday's defeat marked another humbling Wimbledon exit for Errani.
Last year, the Italian went an entire set without winning a point in losing 6-0, 6-4 in the third round to Yaroslava Shvedova of Kazakhstan. Shvedova was the first player in a Grand Slam to achieve a "golden set" by winning 24 straight points.
In another early women's match Monday, former top-ranked Ana Ivanovic of Serbia advanced to the second round with a 7-6 (1), 6-0 win over qualifier Virginie Razzano of France.
The 12th-seeded Ivanovic, a semifinalist in 2007, swept through the second set in 22 minutes, finishing the match with her sixth ace. Another Serb, No. 16 Jelena Jankovic, beat Britain's Johanna Konta 6-2, 7-5.
The weather was cloudy but dry for the beginning of the two-week championships. Among those in the Royal Box were former U.S. Secretary of State Condoleeza Rice and Pippa Middleton, the younger sister of Prince William's wife, Kate.
Also scheduled on Centre Court was No. 2 seeded Andy Murray, playing Benjamin Becker of Germany.