Maria Sharapova
Maria Sharapova of Russia waves to the crowd after beating compatriot Maria Kirilenko during their firs round match at the US OpenReuters

Maria Sharapova showed no mercy towards childhood friend Maria Kirilenko, defeating the fellow Russian 6-4, 6-0 to reach the second round of the US Open on Monday.

Fifth seeded Sharapova trailed 4-2 in the first set, but won the next 10 games to clinch the match in just 90 minutes, and with it set up a second round clash with Romania's Alexandra Dulgheru.

"We spent a lot of time in the juniors away from the courts practicing a lot together, competing against each other," Sharapova said of her relationship with Kirilenko. "We certainly have a big history together."

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The 2006 champion returned to the Arthur Ashe Stadium after she missed last year's tournament due to a shoulder injury. Sharapova has five Grand Slam titles in her kitty and she hopes to add one more in New York. But the Russian admits that it's never easy to defeat your friend on court.

"When you go out on the court, it's always that fine line. Of course you want to be the winner, you have to face that person as a competitor, not someone that you've known for years and developed a friendship with," she said.

"It's always a tricky balance, I guess."

There are a lot of similarities between the two Russians. Both players play right handed and made their debut in 2001. However, they've have experienced different results. Kirilenko has won six career titles while Sharapova has won 32 including five Grand Slams titles.

Meanwhile, two-time US Open champion Venus Williams defeated 43-year-old Kimiko Date-Krumm 2-6, 6-3, 6-3 in the first round. Williams, who is usually one of the older players on court, would have felt a little strange to play someone nine years older than her.

"I was younger today, but when you step out on the court, I don't think anybody thinks about age," said Williams, 34. "If you're out on this tour it means you deserve to be here."

Agnieszka Radwanska, the 25-year-old Pole, thrashed Sheron Fichman of Canada 6-1, 6-0 in just 47 minutes.

"First match is always tricky, but I think everything was working my way - a pretty good start for me," said Radwanska.