Fourth seed Maria Sharapova [Images] overcame an annoying blister and put down a brief fightback by American qualifier Ashley Harkleroad to win 6-1, 7-5 and reach the third round of the Australian Open on Wednesday.

Former world number one and 2004 Wimbledon champion Sharapova saved three set points in the second set as Harkleroad tried to force a deciding set.

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But Sharapova fought off Harkleroad's challenge with two booming serves, showing few signs of the shoulder injury and lack of match practice that had threatened to derail her chances.

The 18-year-old raced through the first set in just 25 minutes as former college player Harkleroad put up little resistance but the Russian sought treatment for a blister on her left foot during the change of ends.

She needed treatment several times more during the second set and later said the blister had put her off her game.

"I played a really good, solid first set and then all of a sudden I got a blister on my foot and the taping made it worse," Sharapova told reporters.

"I started thinking about it and kind of my mind shut down for a little bit," she said.

SERVICE BREAK

Harkleroad gifted her opponent a service break with a double fault at 30-40 in the seventh game of the second set.

However, a distracted Sharapova returned the favour in the next game, giving the American her first service break of the match with two successive forehand errors.

Harkleroad, who had reached the second round for the first time in Melbourne, held three set points on Sharapova's serve in the 10th game of the set.

But an error by the American and then two booming serves allowed Sharapova to stay out of trouble. Harkleroad again handed over a service break with a double fault in the next game before her opponent wrapped up the match in one hour 24 minutes.

Sharapova was annoyed she hadn't ended the match sooner.

"I broke and then at 4-3 I didn't take the opportunity to finish it off," she said.

"It was good for me to realise that once I'm up a break, I need to finish it off rather than just play another four games for the crowd."

Sharapova was, though, grateful for a more competitive match to make up for her lack of time on court since she withdrew from a warm-up event on the Gold Coast last week.

The Russian will play unseeded Croatian Jelena Kostanic in the third round and remains on course for a fourth round match against defending champion and 13th seed Serena Williams [Images].

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