"Well, the wedding. My wife is here", Nadal said as the crowd burst into laughter.
"I trained really hard, obviously I needed some vacation too", said the No.3 seed.
"Of course, I want to do it the best way possible because that's what I am doing since the beginning of my life nearly".
Williams, seeded eighth, won her first title for three years in Auckland last weekend.
Federer said: "I just haven't played proper matches in many, many weeks, and a lot of guys, probably 95 per cent of the guys, are coming here with matches". I think I played a very good level of tennis.
"I went through a couple of things, more than in NY honestly", he explained.
"I don't really know why they want to go the extra mile some of the times. Maybe in a bit more leisurely way".
Roger Federer plays his second-round match at Melbourne Park and, according to his line of thinking, the first few matches he plays in a Grand Slam tournament are as important as the ones at the pointy end. The serving was also solid from Tatsuma Ito as he won over 90% of his service games.
Fiery Italian 12th seed Fabio Fognini survived a major scare to progress 3-6 6-7 (7-3) 6-4 6-3 7-6 (10-5) over big-serving American Reilly Opelka in a fifth-set super-tiebreaker.
Canadian Milos Raonic also had little trouble closing out his rain-delayed encounter over lucky loser Lorenzo Giustino 6-2 6-1 6-3.
Guido Pella, the 22nd seed, ended his three-match losing streak in the first round at Melbourne Park with a 6-3 7-5 6-4 win over John-Patrick Smith.
Olympia came on court for the trophy ceremony, but Serena revealed the toddler had no interest in her achievement.
"Sadly no. She only cares about Play Doh and Qai Qai (her doll)".
Following her medical time out - and some incessant encouragement from the ebullient Conchita Martinez, however, Muguruza was able not only to craft a way back, but return the favour to Rogers with a breadstick and a bagel, taking utter control of the rallies in the third set.
"I think I was just trying to not do something very good, but not doing something very bad".
Fifth seed Dominic Thiem was also a straight-sets victor, beating Adrian Mannarino 6-3 7-5 6-2, while ninth seed Roberto Bautista Agut and former champion Stan Wawrinka successfully reached round two.
Osaka was an early victor as she dismissed Marie Bouzkova of the Czech Republic 6-2, 6-4 in 80 minutes, breaking a net fitting with one powerful serve in the process. A forehand victor gave Nadal a break and 2-0 lead and he took the opening five games before Dellien got on the board, but the Spaniard closed out a 52-minute first set.
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