Ana Ivanovic partly agrees with her ocassional doubles partner Andrea Petkovic that you have to work in order to establish confidence, rather than hoping it just comes naturally.

"It’s a mix," said Ivanovic who will face Peng Shuai in the quarterfinals of the Mercury Insurance Open in San Diego. "The mind is a funny thing and you have to play tricks on it sometimes. One day one thing works and another day something else does. Obviously winning matches helps because you can’t say you are confident and then go and lose every week. You have to have a winning streak, but also if you put the good work in you have different expectations and you are naturally more confident."