"It became a very interesting third set. (It) gave me a lot of information."

"I started to mix it up and trying out things because I had to, I felt, towards the end of the third."

Federer, whose last Grand Slam came at Wimbledon in 2012, will meet Italian Simone Bolelli who needed four sets to get past Juan Monaco.

World No.2 Sharapova continued her flawless start to 2015, despite showing some vulnerabilities during her 6-4 6-1 win over qualifier Petra Martic.

The shoulder injury that plagued the start of her 2014 season was non-apparent and Sharapova was full of confidence.

"I'm in a much more comfortable situation than I was last year, " she said.

"My goal last year at this time was just to play as many matches as I could to get a good feeling."

Sharapova, champion at Brisbane a fortnight ago, looked a little rusty early and was occasionally troubled by the world No. 184.

However the five-time Slam champion immediately made up for her misstep when broken at 5-3 in the first set, taking Martic's next service game and the set.

Serving for the second set, it seemed more of the same woes for Sharapova, but she took her second match point with an ace.

The 2008 champion said she preferred resting the week before the two-week Grand Slam tournaments.

"I'm coming into a Grand Slam hoping to play seven (matches)," she said.

"I don't know (whether playing five the week before too) is physically or mentally smart."

Eugenie Bouchard, who earned a semi-final appearance at last year's tournament, needed only 78 minutes to beat Anna-Lena Friedsam 6-2 6-4.

The 2013 French Open semi-finalist Gulbis was sensationally beaten in a marathon match by Kokkinakis and his 3000-strong army of boisterous fans.

Thannasi Kokkinakis, 18, saved four match points in the fourth stanza but only needed two of his own in the fifth before triumphing 5-7 6-0 1-6 7-6 (7-2) 8-6 in four hours and seven minutes.

Gulbis' unconventional grip was often found wanting against Kokkinakis' flat forehands but he would not blame only that.

"There is not one reason why I lost the match. I do not have a reason why I lost tonight," said Gulbis.

Gulbis lost his way in the second set, including misfiring one serve that bounced into the net, before responding with vengeance in the third. But it in the cut-throat moments, Kokkinakis and his legion of home fans prevailed.

At 6-6 in the final set, Gulbis walked to his seat believing he had just broken Kokkinakis' serve, only for the Australian to challenge the out call and find his ball had caught a sliver of the baseline.

In the final match at Melbourne Park, Wimbledon quarter- finalist Nick Kyrgios overcame a persistent back injury to squeeze past Federico Delbonis 7-6 (7-2) 3-6 6-3 6-7 (5-7) 6-3.