U.S. Open champion Maria Sharapova of Russia beat Timea Bacsinszky of Switzerland 6-4, 6-3 Friday to reach the Zurich Open semifinals and boost her chances of finishing the year atop the world rankings.

Sharapova will next play Katarina Srebotnik of Slovenia, who advanced by defeating Russia's Maria Kirilenko 6-3, 6-2.

The second-seeded Sharapova, playing with foot pain, broke Bacsinszky's opening serve in the first set but then struggled to make the most of further opportunities. She needed four set points to win the first set in 42 minutes.

``I wasn't completely comfortable,'' Sharapova said. ``There were ups and downs. She's a pretty big hitter and has a good backhand.''

Bacsinszky double-faulted to give Sharapova break point on her opening serve of the second set and the Russian converted with a stunning winning volley.

The players traded breaks before another double fault gave Sharapova match point at 5-3. Bacsinszky sent a wild backhand three feet wide to give Sharapova the victory.

``You're up 4-1 with two breaks, you think you've got the match, you get a bit sloppy and start thinking about things you shouldn't be, like `this match should be over already,''' Sharapova said. ``That's what happens when you haven't been playing a lot.''

Sharapova pulled out of a quarter-final in Moscow last week with a right foot injury, which required a few days off. She received a first-round bye in Zurich, while Bacsinszky went through qualifying to reach the main draw.

``It's better after you play more, move around more. After two matches, I'm in a better groove and feeling better,'' Sharapova said.

Sharapova's slim chances of the year-end No. 1 ranking improved Thursday when top-ranked Amelie Mauresmo of France withdrew with a shoulder injury.

Sharapova realistically needs to be champion or runner-up in Zurich because she will only have next week's tournament in Linz, Austria, before the season-ending WTA Championships in Madrid.

Fifth-seeded Martina Hingis of Switzerland, still trying to qualify for Madrid, was scheduled to play third-seeded Svetlana Kuznetsova of Russia later Friday. The winner will face Daniela Hantuchova of Slovakia _ who received a walkover with Mauresmo's withdrawal.

© The Canadian Press, 2007