Roger Federer was made to sweat by Fernando Gonzalez before going through to the semis of the BNP Paribas Open.

Federer's first serve percentage slipped to just 47% in the second set against the 17th seed from Chile, but he bounced back in the decider to win in one hour 49 minutes.

The Swiss second seed will take on Fernando Verdasco in the next round after the 10th-seeded Spaniard survived a second-set scare to claim a 6-4 3-6 6-1 win over Philipp Kohlschreiber.

Andy Murray progressed against 15th-seeded Spaniard Tommy Robredo, who was forced to retire with a wrist injury.

The Scot, seeded four, took the first set 6-2 and was 3-0 up in the second when Robredo threw in the towel.

In the women's event, fourth seed Vera Zvonareva advanced to the semi-finals with a 6-4 6-2 victory over Caroline Wozniacki.

The Russian was hampered by 12 double faults, but saved eight break points and converted four of her own to battle past her Danish opponent, the ninth seed, in one hour 34 minutes.