DUBAI, Feb 24: Defending champion Caroline Wozniacki reached the semi-finals of the Dubai Open here on Thursday, while US Open champion Sam Stosur was beaten by Jelena Jankovic of Serbia.

Caroline Wozniacki ousted Ana Ivanovic of Serbia 6-3, 7-5 in a meeting of former No. 1s, after Jankovic had beaten Stosur 6-4, 6-2 on Thursday.

The 22-year-old Wozniacki eased through the first set and then overcame tougher resistance in the second before overcoming the Serb 1 hour, 33 minutes.

Wozniacki is the highest-seeded player left in Dubai at No. 3 after top-ranked Victoria Azarenka pulled out of the tournament Wednesday because of an ankle injury.

Azarenka unseated Wozniacki from the No. 1 ranking last month by winning the Australian Open.

Wozniacki will play Julia Goerges after the unseeded German defeated Daniela Hantuchova of Slovakia 4-6, 6-3, 6-4.

Earlier, the eighth-seeded Jankovic was in control throughout the match as the fourth-seeded Stosur struggled with her game.

The Australian seemed to rush her shots for much of the first set, hitting the ball early and returning it long and wide. Stosur broke Jankovic early in the second, but the Serb broke right back and then pulled ahead 5-2 before wrapping up the match in 1 hour, 30 minutes.

Jankovic will meet fifth-seeded Agnieszka Radwanska in the semi-finals.

Results (x denotes seeding): Quarter-finals: Jelena Jankovic (SRB x8) bt Samantha Stosur (AUS x4) 6-4, 6-2; Agnieszka Radwanska (POL x5) bt Sabine Lisicki (GER x9) 6-2, 6-1; Caroline Wozniacki (DEN x3) bt Ana Ivanovic (SRB) 6-3, 7-5; Julia Goerges (GER) bt Daniela Hantuchova (SVK) 4-6, 6-3, 6-4.

ISNER IN QUARTERS MEMPHIS (Tennessee): Top-seeded John Isner fired 22 aces in a 7-6 (7-3), 6-4 victory over Donald Young on Thursday to reach the quarter-finals of the $1.375 million ATP and WTA Memphis Open.

He will now face Austrian Jurgen Melzer, a 2-6, 6-3, 7-6 (7-5) winner over Croatian Ivan Dodig, in the quarter-finals.

US wildcard Sam Querrey reached his first quarter-final of the year with a 7-6 (7-4), 6-4 victory over seventh-seeded Kevin Anderson.

Querrey, who won the Memphis title in 2010, broke Anderson twice to improve book a quarter-final clash with third-seeded Czech Radek Stepanek, a 4-6, 6-3, 7-6 (7-4) winner over American Ryan Sweeting.

Poland’s Lukasz Kubot reached his first quarter-final since last July in Stuttgart with a 7-6 (7-5), 6-2 victory over Germany’s Philipp Petzschner. He will play compatriot Benjamin Becker, a 7-6 (7-4), 6-4 winner over Belgian Xavier Malisse.

Results: Men’s (second round): Jurgen Melzer (AUT) bt Ivan Dodig (CRO) 2-6, 6-3, 7-6 (7-5); Radek Stepanek (CZE x3) bt Ryan Sweeting (US) 4-6, 6-3, 7-6 (7-4); Sam Querrey (US) bt Kevin Anderson (RSA x7) 7-6 (7-4), 6-4; Olivier Rochus (BEL) bt Ryan Harrison (US) 6-4, 7-5; Lukasz Kubot (POL) bt Philipp Petzschner (GER) 7-6 (7-5), 6-2; Benjamin Becker (GER) bt Xavier Malisse (BEL) 7-6 (7-4), 6-4; John Isner (US x1) bt Donald Young 7-6 (7-3), 6-4; Milos Raonic (CAN x4) bt Sergiy Stakhovsky (UKR) 6-4, 6-4.

Women’s (quarter-finals): Vera Dushevina (RUS) bt Stephanie Foretz Gacon (FRA) 3-6, 6-3, 6-1; Marina Erakovic (NZL x4) bt Michaella Krajicek (NED) 6-4, 6-7 (2-7), 6-4; Alberta Brianti (ITA) bt Varvara Lepchenko (US) 7-5, 6-3; Sofia Arvidsson (SWE) bt Lesia Tsurenko (UKR) 6-2, 7-6 (11-9).

SIMON, VERDASCO, MONACO FALL BUENOS AIRES: Seeded players Gilles Simon of France, Fernando Verdasco of Spain and local favourite Juan Monaco were knocked out in the second round of the Buenos Aires Open here on Thursday.

Carlos Berlocq of Argentina beat the third-seeded Simon 6-2, 6-1 and Igor Andreev of Russia downed No. 7 Verdasco 7-6 (3), 6-3 at the clay-court tournament. Argentine David Nalbandian defeated No. 5 Monaco 6-3, 6-1.

One seeded player survived: No. 2 Nicolas Almagro of Spain had an easy time beating Federico Delbonis of Argentina 6-3, 6-2. Results:

Second round: Igor Andreev (Russia) bt 7-Fernando Verdasco (Spain) 7-6(3), 6-3; Carlos Berlocq (Argentina) bt 3-Gilles Simon (France) 6-2, 6-1.—Agencies