DOHA, Qatar (AP) -- U.S. Open champion Sam Stosur reached her first semifinal of the year, defeating Monica Niculescu 6-2, 2-6, 6-3 Friday at the Qatar Open.

In another quarterfinal, top-ranked Victoria Azarenka swept aside Yanina Wickmayer of Belgium 6-0, 6-4 for her 15th straight win.

After losing in the first round of her home Australian Open, Stosur has won three straight matches in Doha. Her latest victory came against a Romanian opponent who uses lots of spin and hits a two-handed backhand and forehand.

"It's a really good feeling,'' Stosur said. "I guess it's still only February, so to bounce back relatively quickly is always pleasing. Yeah, it's definitely nice to be on the winning side than not.''

Stosur jumped to 5-0 en route to winning the first set. But Niculescu responded in the second, breaking Stosur twice to go up 4-1 to even the match.

Stosur regained the momentum in the third, leading 3-0 only to see Niculescu take advantage of errors to make it 3-3. But with Stosur serving at love-30 in the seventh game, Niculescu failed to capitalize. She missed an easy volley to let Stosur back in the game, and Stosur then hit a forehand in the corner to go up 4-3. She ran off the final two games.

"For sure, I got off to a really good start and wasn't, you know, under too much pressure at all,'' Stosur said. "Then early in that second set, I feel like I missed some of those opportunities. I think it's one of those matches where, when you are in control, you have to keep going and keep going and keep going.''

Azarenka said she played a "perfect set'' to go up 6-0, but the second set was much more competitive. The two players traded breaks throughout until 4-4. The Belarusian then ran off the last two games, winning a love service game to close out the match.

"Second set, I had opportunities in every single game. I just couldn't really convert them,'' Azarenka said. "But, you know, it's important the way I finished the second set. It was the same way I started the match.''

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