Juan Ignacio Chela weathered a stiff challenge from Stanislas Wawrinka in a gruelling five-setter while Carlos Moya overcame a mid-game slump against Ernests Gulbis to advance to the quarterfinals of the US Open on Monday.

Argintine Chela, seeded 20th here, after winning the first 6-4, went on to lose the next two 2-6, 6-7 (6/8) as his Swiss opponent mounted a great comeback. Chela, however, regrouped well to clinch the final two sets 6-1, 6-4 to come out a winner.

Moya defeated his Lativian rival 7-5, 6-2, 6-7 (5/7), 6-4.

Meanwhile, Roger Federer responded to a stellar start by Feliciano Lopez with an even better finish to advance to the quarterfinals and a clash with old foe Andy Roddick.

Three-times defending champion Federer earned a match-up with 2003 champion Roddick by defeating Lopez 3-6, 6-4, 6-1, 6-4 in a two-hour slugfest on Arthur Ashe Stadium.

The 60th-ranked Lopez had Federer on his heels early, winning the first set with five aces and 11 winners. His dazzling display continued until Federer scored a break in the 10th game to win the second set, and Lopez never recovered after that.

Next up for Federer will be fifth-seeded Roddick, who was leading 7-6, 2-0 when ninth-seeded Czech Tomas Berdych retired with nausea and breathing problems.

Also advancing were fourth seed Nikolay Davydenko of Russia and 10th-seeded Tommy Haas of Germany. On the women's side, winners included sixth seed Russian Anna Chakvetadze and Israeli Shahar Peer.

Kuznetsova needed only 74 minutes to dispose of Victoria Azarenka of Belarus 6-2, 6-3 to reach the Open's last eight for the first time since winning the title in 2004.

She now faces unseeded Agnes Szavay of Hungary, who beat Ukraine's Julia Vakulenko 6-4, 7-6.

Second-set wobble

Chakvetadze had 23 errors during a second-set wobble but defeated Austrian teenager Tamira Paszek 6-1, 7-5, and now faces Peer for a place in the semifinals.

Haas scored a mild upset when he defeated number six American James Blake 4-6, 6-4, 3-6, 6-0, 7-6 (7-4), while Davydenko scored a a 6-1, 6-3, 6-4 win over Korean Lee Hyung-taik. In a doubles upset, top seeds Bob and Mike Bryan were beaten 7-5, 6-4 in the quarterfinals by 10th seeds Simon Aspelin of Sweden and Julian Knowle of Austria.

Sania-Bhupathi lose

Sania Mirza crashed out of the mixed doubles event after a straight-set loss in the last-eight stage, adds PTI.
Sania and Mahesh Bhupathi were outplayed 4-6, 1-6 by Belarussians Victoria Azarenka and Max Mirnyi.