By Julian Linden
MELBOURNE (Reuters) - Justine Henin passed the first serious test in her comeback to the Australian Open when she defeated Russia's Elena Dementieva 7-5 7-6 on Wednesday in a high quality match of unrelenting tension.
The Belgian, a wildcard entry as she does not even have a ranking yet, dispelled any doubts about whether she can mix it with the best after coming out of retirement with a performance reminiscent of when she was world number one.
Fourth seed Juan Martin del Potro also provided a reminder of the fighting qualities that enabled the towering Argentine to topple Roger Federer in last year's U.S. Open final when he beat American James Blake 6-4 6-7 5-7 6-3 10-8.
Rafa Nadal erased any lingering concerns about his fitness with an effortless 6-2 6-2 6-2 win over Slovakia's Lukas Lacko that brought a rare smile to the face of the number two seed after a year plagued by injuries and self doubt.
"I think I did well, no?," the Spaniard told reporters. "I think I played the right way. A very good match, yeah."
Kim Clijsters, Svetlana Kuznetsova and Dinara Safina had no problems booking spots in the third round of the women's draw while Andy Roddick and Andy Murray did likewise in the men's.
Henin was inspired by compatriot Clijsters's fairytale win at last year's U.S. Open to make a comeback and said Wednesday's victory over the world number five vindicated her decision.
"I wouldn't believe I would live these kind of emotions again," she said in a courtside interview. "But the tournament is not over for me yet."
Clijsters, who took a two-year break before returning to the sport last August, was given an easier workout by Thailand's Tamarine Tanasugarn and was able to raise her game when necessary in a 6-3 6-3 victory while Kuznetsova beat fellow Russian Anastasia Pavlyuchenkova 6-2 6-2.
They are scheduled to meet in the fourth-round with the winner to play Henin should the trio all keep winning in one of the most open grand slam events in decades.
"This is for real," third seed and French Open champion Kuznetsova said. "This is for what you play for."
Safina, last year's runner-up, overcame a minor stumble when serving for the match in her 6-3 6-4 victory over Barbora Zahlavova Strycova.
The world number two is in the bottom quarter, safely away from the Belgians, Russians and Williams sisters.
Danish fourth seed Caroline Wozniacki made a belated start to her campaign at Melbourne Park, defeating Canada's Aleksandra Wozniak in a first-round match that was shuffled back because of rain on the opening day.
Roddick eased to a 6-3 6-4 6-4 win over Brazil's Thomaz Bellucci but the match ended on a sour note when the American argued with the chair umpire over a line call in the final game, risking the possibility of a fine for foul language.
"I don't do it for entertainment. I do it because I strongly believe what I feel," Roddick later explained. "I think if I believe in something strongly enough, I'm pretty outspoken about it."
Murray was better behaved but unhappy with himself after struggling with his serve in the windy conditions on Margaret Court Arena during his 6-1 6-4 6-3 victory over France's Marc Gicquel.
"This is the highest level of the sport. That's going to happen," he said.
Britain's top female Elena Baltacha also made it through to the third round by beating Ukraine's 30th seed Kateryna Bondarenko 6-2 7-5 but there was no more luck for Ireland's new sporting hero Louk Sorenson. He went down to American John Isner 6-3 7-6 7-5.
(Editing by Pritha Sarkar)