Defending Australian Open champion Kim Clijsters and 2011 runner-up Li Na set course for a rematch of last year's final Monday as both started with wins at the season's first grand slam. Belgium's Clijsters saw off Portugese qualifier Maria Joao Koehler 7-5, 6-1, soon after Li won a tough first round match against Ksenia Pervak of Kazakhstan 6-3, 6-1. On a day when the big guns came out firing, third seeded Belarusian Victoria Azarenka demolished Britain's Heather Watson 6-1, 6-0, and 2010 French Open champion Francesca Schiavone crushed Spaniard Laura Pous-Tio 6-1, 6-3. Clijsters, who plans to retire this year, had returned to the scene of her 2011 triumph under an injury cloud after pulling out of the Brisbane International two weeks ago with a hip problem. She was forced to work hard in the early stages by the unknown Koehler, who was playing her first ever main tour match outside Portugal. But, when serving at 5-6, Koehler's inexperience told and Clijsters attacked, quickly racing to 0-40, then wrapping up the first set courtesy of a double-fault. Clijsters seized control and broke twice more in the second set to cruise to a comfortable win, keeping her on track for a potential fourth-round clash with Li.   "I'm feeling good and I'm happy to say that (the injury) is all behind me," the 28-year-old world number 14 said. Like Clijsters, Li was also made to work hard in the first set before taking control in the second, later admitting she had suffered in the hot conditions. "I was feeling at the end of the first set really the heat on the court," Li said. "Also I was feeling no air. I couldn't breathe. Like I was feeling like, what's going on?" Earlier, in the first match on centre court Azarenka dominated Watson as she pressed her claims for a maiden grand slam win. The Belarusian, who won last week's Sydney International and is unbeaten in 2012, needed just 67 minutes to overwhelm Watson and move into a second round clash against Australia's Casey Dellacqua. "I think it was a good performance," Azarenka said. "There are a few things for me that I have to work on tomorrow to be better in my second round, but you know, I take what I get. I cannot complain." The highest profile casualty on day one was 19th seed Flavia Pennetta, who fell to Russian qualifier Nina Bratchikova 6-3, 1-6, 6-2. Pennetta injured her back in the season-opening tournament in Auckland and subsequently withdrew from Sydney last week. She battled hard but eventually succumbed in one-and-a-half hours. Eighth seed Agnieszka Radwanska came from a set down to beat colourful American Bethanie Mattek-Sands 6-7 (10/12), 6-4, 6-2 in a match lasting three hours exactly. Slovakian Daniela Hantuchova, the 20th seed, defeated US qualifier Varvara Lepchenko 4-6, 6-3, 6-2, while 16th seed Peng Shuai ensured a good day for the Chinese with a 6-3, 6-4 win over France's Aravane Rezai. Meanwhile Greece's Eleni Daniilidou ended the hopes of 41-year-old Kimiko Date-Krumm 6-3, 6-2. The Japanese veteran became the second oldest player to contest the Australian Open women's singles in the open era, after the 44-year-old Beverley Rae in 1974, but she couldn't match her Greek opponent, who wrapped up the encounter in one hour and 24 minutes. Date-Krumm's fellow countrywoman Ayumi Morita also bowed out in the first round, at the hands of Petra Cetkovska, the Czech 32nd seed winning 3-6, 6-1, 7-5. Other seeds to win were Germany's Julie Goerges (22), who beat Polona Hercog of Slovenia 6-3, 7-6 (7/3) and Spain's Anabel Medina Garrigues (26), who progressed with a comfortable 6-3, 6-3 win over Czech Eva Birnerova.