MELBOURNE, Australia -- Roger Federer returned from a six-month layoff to beat fellow 35-year-old Jurgen Melzer just before midnight on day one of the Australian Open, agreeing it felt a bit like coming home.
The 17-time major winner hadn't played at tour level since Wimbledon, giving his injured left knee time to heal.
He served 19 aces and had only one double-fault in a 7-5, 3-6, 6-2, 6-2 win on Monday over Melzer, but dropped serve three times and had moments of frustration.
"It's nice to be playing normal tennis again," he said. "It was a long road (but) I'm in the draw, which is a beautiful thing."
Federer surprised himself by still feeling nervous when the match started, and he took a while to settle down.
"I was fine all day ... I felt fine. Then I hit four frames in a row," he said. "It was like, `Whew, it's not as easy as I thought it was going to be," he said. "Think I struggled for a while to find that groove, that rhythm."
Federer has won four Australian titles and reached the semifinals or better in 12 of the previous 13 years, and making himself at home on Rod Laver Arena.
He'll play another qualifier in the second round after Noah Rubin beat Bjorn Fratangelo.
It wasn't always easy, but Andy Murray claimed his first win as a top-seeded player in a Grand Slam tournament with a 7-5, 7-6 (5), 6-2 victory over Illya Marchenko of Ukraine.
Murray, who took over the No. 1 ranking from Novak Djokovic late last year, has never won the Australian Open despite being a five-time finalist here, including the past two years. Marchenko had 46 winners in the match compared to Murray's 25, but Murray helped his cause by breaking the Ukrainian player's service in six of eight opportunities.
And Marchenko made 62 unforced errors, compared with Murray's 27.
"I've never won here -- I'm going to try to change that this year," Murray said.
Kei Nishikori overcame an error-plagued performance Monday to beat Andrey Kuznetsov in an opening-round struggle.
No. 5 Nishikori fell into an early hole and failed to capitalize on a 5-2 lead in the fourth-set tiebreaker, but came back to win 5-7, 6-1, 6-4, 6-7 (6), 6-2 in 3 hours and 34 minutes.
"Wasn't easy," Nishikori said in his on-court interview. "Should have finished in four sets, but really happy to finish the first round."
The taxing performance was surprising; just two weeks ago, Nishikori reached the Brisbane International final, where he dropped a tight three-set affair to Grigor Dimitrov. Nishikori, who has been touted as a future Grand Slam winner ever since he entered the tour-level scene full time in 2011, solidified himself as a legitimate threat to the Big Four last season. He beat Rafael Nadal at the Rio Olympics and weeks later made the US Open semifinals.
Nishikori, a three-time quarterfinalist here in Melbourne, including the past two years, met Kuznetsov twice last year in Grand Slam play, winning both matches in straight sets. But the Japanese player struggled with consistency Monday. In the opening set alone, he committed 18 unforced errors and finished the match with 52 -- against 53 winners.
Nishikori improved to 15-5 in five-set matches. Only Tommy Robredo and Djokovic have better five-set records among active players. Nishikori looked sharp in the final frame, moving through the court much more fluidly than his Russian opponent, a positive sign considering the overall struggle.
"Had to reset after the fourth set," Nishikori said. "Definitely, I needed to relax my mind going into the fifth. But I like playing in front of these fans; I felt comfortable."
Kuznetsov was hoping to build off a strong performance last year in Melbourne, where he reached the round of 16, a Grand Slam best. But the unlucky draw pitted him against a player who came into the season expecting big things.
In early January, Nishikori told ESPN.com that he finally felt poised and in position to break through with what he described as a perfect combination of aggressiveness and acumen.
"There has to be balance, and I think I'm getting better and better," Nishikori said.
Nishikori could potentially meet Federer in the fourth round and Murray in the semifinals.
US Open champion Stan Wawrinka scraped into the second round after beating 35th-ranked Martin Klizan of Slovakia 4-6, 6-4, 7-5, 4-6, 6-4.
In the ninth game of the fifth set, fourth-seeded Wawrinka smashed a soft half-volley from Klizan straight back into the Slovakian's body, clipping the frame and just missing his groin.
Wawrinka was concerned enough about his opponent that he jumped over the net to make sure Klizan was OK, but the match continued without much delay.
Wawrinka held serve in that game to lead 5-4, then broke Klizan in the next game to clinch the match in 3 hours, 24 minutes.
There were 32 break-point chances in the match, with Wawrinka converting six chances to Klizan's five.
There were two early retirements in the men's draw. No. 10-seeded Tomas Berdych, the 2010 Wimbledon finalist, was leading 6-1 when Luca Vanni retired from their match, and Jeremy Chardy was leading 4-0 when Nicolas Almagro retired with an injured right calf muscle in the first set.
"I'll take it -- an easy match never hurts at a long tournament like this," Chardy said.
In other action, seventh-seeded Marin Cilic struggled before beating Jerzy Janowicz 4-6, 4-6, 6-2, 6-2, 6-3, and No. 14 Nick Kyrgios returned from his suspension for underperforming in Shanghai last year by racing through a 6-1, 6-2, 6-2 win against Gastao Elias. Ryan Harrison beat Nicolas Mahut 6-3, 6-4, 6-2.
Other men advancing included No. 12 Jo-Wilfried Tsonga (the 2008 finalist), No. 19 John Isner, No. 23 Jack Sock, No. 27 Bernard Tomic, No. 29 Viktor Troicki and No. 31 Sam Querrey.
No. 16 Lucas Pouille lost to Kazakh qualifier Alexander Bublik and No. 26 Albert Ramos was beaten by Slovakian qualifier Lukas Lack.
The Associated Press contributed to this report.