* Djokovic into second round
* Sharapova, Venus, Li progress in style
* Monaco first seed to fall
MELBOURNE, Jan 14 (Reuters) - Novak Djokovic served up only flashes of his best tennis on the opening day of the Australian Open but took a comfortable first step on the path he hopes will lead to an unprecedented hat-trick of titles at Melbourne Park in two weeks' time.
Perhaps keeping energy in reserve for the battles that lie ahead, the world number one's workmanlike 6-2 6-4 7-5 victory over Frenchman Paul-Henri Mathieu on Monday summed up a day where the year's first grand slam failed to really fire.
"It was a good performance for a first round," said the top seed, who will play American Ryan Harrison in the second round.
"There are some few adjustments that I need to make and get a little bit sharper on the court. But it's expected in the first match you're still not a 100 percent on the court."
While Djokovic only roused himself when necessary, Maria Sharapova was ruthless as she swept aside any fears about her fitness with a thumping 6-0 6-0 win over compatriot Olga Puchkova on Rod Laver Arena.
American Venus Williams and China's Li Na, both former losing finalists, also enjoyed emphatic wins to breeze into the second round, while in-form fourth seed Agnieszka Radwanska extended her perfect start to the year to 10 matches.
Upsets are often the catalyst that jolt a tournament into life but Argentina's Juan Monaco was the first seed to fall in the early evening and his 7-6 6-1 6-1 defeat was as much down to hand and leg injuries as Russian Andrey Kuznetsov.
Lleyton Hewitt did his best to produce another shock in front of a partisan night crowd but eighth seed Janko Tipsarevic brought a rapid end to the Australian's 17th appearance at his home open with a 7-6 7-5 6-3 victory.
Serbian Djokovic only hit top gear twice in his match against Mathieu - when he faced three break points in the second set and again when the third set looked destined for a tiebreak.
On the first occasion he rustled up three aces to get himself out of trouble and on the second, he produced a couple of exceptional winners to break the Frenchman and set up victory in an hour and 42 minutes.
"I felt I was in control of the match in the opening two sets then he started playing better," said Djokovic, who would set an open era record with three successive titles.
"It was tough to break. But in the end ... I made some good shots and managed to go through straight sets."
With Andy Murray and Roger Federer not beginning their campaigns until Tuesday and Rafa Nadal absent injured, Monday was an opportunity for those players just outside the elite of the men's game to strut their stuff.
David Ferrer duly continued the form which won him a fourth Auckland Open title on Saturday to beat Olivier Rochus 6-3 6-4 6-2, while fifth seed Tomas Berdych also progressed with a 6-3 7-5 6-3 win over American Michael Russell.
Despite the record temperatures which have gripped Australia for the last couple of weeks, the Australian Open opened to a mild morning in Melbourne.
There was nothing mild about Sharapova's demolition of Puchkova on Rod Laver Arena, however, and the Russian powered her way into the second round in just 55 minutes.
Firing winners at will, particularly off the forehand, the 2008 champion showed no signs of the collar bone injury that caused her to pull out of the Brisbane warm-up.
"I was happy with the way I started, considering I didn't play any matches coming in," the 25-year-old said. "It was just one of those matches where I didn't try to worry about her too much, I just tried to think about what I had to do."
Williams could meet Sharapova in the third round and proved she might be a handful for the second seed by winning 12 successive games to beat Kazakh Galina Voskoboeva 6-1 6-0.
It was 10 years ago that Williams lost her only Australian Open final to her sister Serena, who gets her campaign underway on Tuesday.
Pole Radwanska, winner of back-to-back warm-up events in Sydney and Auckland, battled through a tricky first set and whipped through the second to beat Australian wildcard Bojana Bobusic 7-5 6-0.
Li lost to Radwanska in Sydney last week to end her own winning streak at eight matches, but the former French Open champion continued to thrive under the guidance of her new coach with a 6-1 6-3 victory over Sesil Karatantcheva.
"He's not only a teacher about tennis, not only about technique, he's also helping me get my mind stronger on court," Li said of Justine Henin's former mentor Carlos Rodriguez.
Mental fragility has contributed to Sam Stosur's poor showings at her home grand slam and the ninth seed again failed to convince in a 7-6 6-3 win over Chang Kai-chen of Taiwan.
"I desperately wanted to win out there today, but I didn't necessarily feel it any more than my first rounds in grand slams," said the Australian, who was knocked out in the first round last year and at her warm-ups in Brisbane and Sydney. (Editing by Toby Davis)