Serena Williams overcame a sloppy first-set performance to book a place in the quarter-finals of the Internazionali d'Italia with victory over Christina McHale.

The world number one was well below her best in the early stages of Thursday's match in Rome and appeared likely to be punished as McHale impressed with a series of impressive strokes off each wing. However, three-time champion Williams managed to take the opening set in a tie-break, despite racking up 27 unforced errors, and then breezed through the second to triumph 7-6 (9-7) 6-1 as her opponent wilted.

McHale had chances to break in each of Williams' first three service games and eventually gained the upper hand at the eighth time of asking when the top seed overhit a forehand.

Williams' frustration was clear as she continued to struggle, the 34-year-old turning her back at one point as McHale waited for a high ball to drop before putting away a simple smash.

However, the underdog faltered when attempting to serve out the set, prompting a cry of delight from the other side of the net, and Williams duly took her third chance to claim the breaker after McHale had missed a sole opportunity at 7-6.

The second set failed to offer the same level of drama, with McHale, who turned 24 on Wednesday, unable to maintain her level of performance and swiftly falling to defeat.

Results - Women's 3rd round

Serena Williams (USA x1) bt Christina McHale 7-6 (9/7), 6-1.

Svetlana Kuznetsova (RUS) bt Daria Gavrilova (AUS) 6-2, 2-6, 6-3.

Timea Bacsinszky (SUI x11) bt Carla Suarez Navarro (ESP x8) 5-7, 7-5, 6-2.

Garbine Muguruza (ESP x3) bt Jelena Ostapenko (LAT) 6-1, 6-4.

Irina-Camelia Begu (ROM) bt Daria Kasatkina (RUS) 6-1, 6-4.