Auckland Classic champion Verdasco also makes second round, with straight-sets win over Bautista Agut
Australian Open Day 2: Federer begins title defence with win and Djokovic through to Round 2
Defending champion Roger Federer breezed past Aljaz Bedene in straight sets to launch his Australian Open campaign on Tuesday.
The Swiss second seed won 6-3, 6-4, 6-3 and will next play German Jan-Lennard Struff in the second round.
Djokovic makes memorable comeback
Six-time champion Novak Djokovic looked his old self as he powered to a convincing first round victory at the Australian Open on Tuesday on his return from an elbow injury, saying he felt "great".
The 12-times Grand Slam winner, seeded an unfamiliar 14, was too strong for American Donald Young, winning 6-1, 6-2, 6-4 in 1hr 51min on Margaret Court Arena.
The Serbian former world number one has been out of action for six months.
But he looked in good fettle as he worked his way into the second round where he will play Frenchman Gael Monfils.
Djokovic, wearing a flesh-coloured protective guard on his right serving elbow, saluted the cheering crowd as he won on his sixth match point.
"It felt great to be back on the court and compete again. It's been a while. Obviously, you don't know how you're going to start off," he said.
"I was putting a lot of hours on the court in the last couple weeks, and I played a lot of practice sets, and I had only one match leading up to this tournament in Kooyong.
"In more or less all of these practice sessions, I could feel that I'm hitting the ball well. So I was hoping this is going to obviously continue and be transferred into the first round of Australian Open.
"The first two sets went extremely well, considering that I haven't played for six months. The third was up and down a little bit, but in general it was a great performance."
Zverev wins long slog with Fabbiano
Young German star Alexander Zverev needed a hard-fought three sets to get through his opening encounter at the Australian Open on Tuesday and spoke of his search for greater consistency.
The world No 4 spent two hours and 22 minutes on Rod Laver Arena before claiming a 6-1, 7-6, 7-5 win over 73rd-ranked Italian Thomas Fabbiano.
Zverev, at the vanguard of the "NextGen" brigade, will face fellow German Peter Gojowczyk in the second round.
While the 20 year old won five titles and was one of just four players to beat Roger Federer last year, he has yet to get beyond the fourth round at a grand slam.
"I think last year I was pretty consistent, apart from the end of the year," Zverev said. "I think my game is getting more consistent with age as well. I think that's also something that is a factor of maturity.
"So I'm just trying to get better every single day, and that's what I'm here for."
Zverev said he was expecting a tough scrap against Fabbiano.
"That's what he does. That's what he's known for on tour, to be competitive, to fight for every single point, play well from the baseline," he said.
"He's like a Diego Schwartzman-type of player. So they are always not easy to beat, especially in first rounds.
"I was a bit surprised with his serve and how well he was serving. But apart from that, I was looking forward to a tough match."
Zverev served up 17 aces among his 47 winners and broke Fabbiano's serve five times, while saving 12 break points.
He said of his next opponent Gojowczyk: "He's someone who plays really well on the hard courts.
"I think he played well in Auckland, as well. Obviously, a player that's very well informed."
Zverev was ousted in the third round in Melbourne in 2017 and could face a potential third-round clash against his older brother Mischa if he gets past Gojowczyk.
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Wawrinka wins first match after surgery
Former champion Stan Wawrinka was taken to four sets before winning his first match since knee surgery in July at the Australian Open on Tuesday.
The three-time grand slam winner downed Ricardas Berankis 6-3, 6-4, 2-6, 7-6 on Hisense Arena.
It was a confidence booster for the 2014 Melbourne Park champion who had a troubled lead-in to the year's opening grand slam, pulling out of an exhibition event in Abu Dhabi.
The Swiss star, who defeated Rafael Nadal to win in 2014, has slipped to nine in the world rankings, having not played since his first-round Wimbledon loss to Russian Daniil Medvedev six months ago.
"It was a tough battle and I'm really happy to win my first match here after six months out," Wawrinka said.
Vercasco triumphs over Bautista Agut
Auckland Classic champion Fernando Verdasco also made the second round, with a straight-sets win over 20th seed Roberto Bautista Agut.
But Raonic, who has made at least the last eight over the past three years in Melbourne, was bundled out by 86th-ranked Slovakian Lukas Lacko in four sets.
It was his earliest grand slam exit in seven years as he fights back from a wrist injury.
Underprepared Raonic is out
Milos Raonic was dumped out of the Australian Open by Lukas Lacko on Tuesday in his earliest exit at grand slam for seven years.
The 86th-ranked Slovakian defeated the 22nd seeded Canadian 6-7, 7-5, 6-4, 7-6 in 3hr 22min on Show Court 3.
It was Raonic's worst performance at a major since losing in the first round at Roland Garros in 2011.
The Canadian, a semi-finalist in Melbourne two years ago, was fighting to make up for lost time after wrist and calf injuries last year and an early exit at the lead-in Brisbane International tournament this month.
"I wasn't sharp and I struggled physically, thankfully not from injury, but from fitness and preparedness and that caught up with me a lot," Raonic said.