World number one Roger Federer survived an inconsistent form to beat Florent Serra 7-6 (7-2), 7-6 (7-3) on Monday in the third round of the WTA and ATP tournament in Miami, the United States.

Switzerland's Roger Federer returns this shot to France's Florent Serra during their match at the Sony Ericsson Open tennis tournament in Key Biscayne, Florida, March 29, 2010. [Xinhua/Reuters Photo]

Federer lost serve three times, each time when he led. He committed 35 unforced errors to 32 for Serra.

But Federer won eight consecutive service points in the tiebreakers and closed out the victory with a service winner.

The top-seeded woman, Svetlana Kuznetsova, was hampered by a right shoulder injury and lost to Marion Bartoli 6-3, 6-0 in the fourth round.

Kuznetsova, the 2006 champion, required treatment from a trainer three times during the match and won only eight points in the second set.

Mardy Fish reached the fourth round with his second consecutive win over a seeded opponent, beating No. 29 Feliciano Lopez 7-5, 6-3. Fish upset defending champion Andy Murray in the second round.