Simona Halep survived a sluggish performance to book a spot in the quarter-finals of the Cincinnati Open with a 4-6 6-4 6-2 victory over Andrea Petkovic

The locals were offered an early sign of what was to come as both players started the match by securing breaks.

Halep, in particular, appeared to be vulnerable on her serve but she dominated the longer rallies for much of the opening set until Petkovic raised hopes of an upset by clinching the lead with a break in the 10th game.

Serving troubles were often the key factor in a dramatic clash as both players lost their serve again, before Halep displayed her class in a couple of crucial points to pull ahead.

Petkovic continued to battle impressively as her rival stepped up the tempo, but Halep held her nerve to convert set point at the third attempt as the third seed fought back to draw level.

A similar pattern emerged in the decider as each player earned a break inside the opening four games.

Halep was far from convincing on serve, but a couple of mistakes from Petkovic at key stages handed her a double break and the Romanian capitalised on the collapse to serve out for the win.