Novak Djokovic's Boris Becker era got underway in low-key fashion as a clinical Serena Williams and Li Na showed their intent on an eventful first day at the Australian Open Monday.

As temperatures soared and big names fell by the wayside, Djokovic and Williams dodged the day-time heat to open their campaigns with wins on a balmy evening at Rod Laver Arena.Williams put Australian teenager Ashleigh Barty to the sword but Djokovic, playing his first competitive match under new coach Becker, was surprisingly sloppy as he took nearly two hours to subdue Slovakia's Lukas Lacko."It's my first competitive match this season after a five to six week break and I was rusty in the first two sets," admitted the Serb, seeking a fourth straight Melbourne title."I was struggling to find rhythm on my backhand side."Despite the relatively below-par 6-3, 7-6 (7/2), 6-1 win, Djokovic was in no danger of joining Petra Kvitova, Venus Williams and Sara Errani among the casualties on day one.View galleryChina's Li Na plays a shot against Croatia's …China's Li Na plays a shot against Croatia's Ana Konjuh during their women's singles mat …The unseeded Venus Williams, wilting in the midday heat, lost to Russia's Ekaterina Makarova over three sets while Italian seventh seed Errani went out to Julia Goerges.And former Wimbledon champion Petra Kvitova, the sixth seed, fell victim to a sensational upset when she was ambushed 6-2, 1-6, 6-4 by unheralded Thai Luksika Kumkhum."I think that probably I wanted it too much, and then everything just fell down," said the crestfallen Czech.China's Li, last year's runner-up, escaped the 30 Celsius (86 Fahrenheit) heat by racing through her opener against 16-year-old Ana Konjuh 6-2, 6-0."I think it was very lucky we played today. Tomorrow will be the worse," said Li, adding that she moved her practice on Tuesday, when temperatures are forecast to soar, to an earlier slot. "I didn't want to kill myself on the court," she said.The ice packs were already out on day one with the Netherlands' Kiki Bertens needing attention and having her blood pressure measured during her defeat to former world number one Ana Ivanovic.Top 10 men's players Stanislas Wawrinka, David Ferrer, Tomas Berdych and Richard Gasquet went through, accompanied by Jerzy Janowicz and Russian veteran Nikolay Davydenko.In-form Wawrinka had it easy when Andrey Golubev retired when a set down, while Ferrer and Berdych won in straights against Alejandro Gonzalez and Aleksandr Nedovyesov respectively.Gasquet shrugged off a rib problem which kept him out of last week's Kooyong Classic final to beat fellow Frenchman David Guez in straight sets.And Britain's Heather Watson and Laura Robson both fell at the first hurdle, leaving Wimbledon champion Andy Murray as the country's lone singles representative.Officials had words of reassurance for the players ahead of Tuesday's expected high temperatures, saying nobody had ever died from extreme heat at a tennis tournament."We have had players almost die from drinking too much. So the danger is overdrinking, not underdrinking and becoming dehydrated," said the tournament's chief medical officer, Tim Wood."Given the length of time tennis matches generally go for and the sweat rate of most normal, healthy athletes, they won't get to a state where they get too critically dehydrated."The tournament has a well-earned reputation for extreme heat. In 2009, Djokovic became a high-profile casualty when he pulled out of his title defence in the quarter-finals, complaining of heat exhaustion.Djokovic is bidding to become the first player in the Open era to win the title four times in a row, while Williams can equal Chris Evert and Martina Navratilova's haul of 18 majors.(yahoo.com)ANN.Az