' coach Patrick Mouratoglou believes her mixed doubles adventure with Andy Murray
has left her in prime shape to win her 24th Grand Slam singles title.
The 37-year-old American came into Wimbledon
having not played since the French Open
, when she was hampered by knee problems.
But she has built her form gradually during the fortnight and her French coach attributes this partly to her doubles.
'For sure it is helping her singles,' said Mouratoglou on Wednesday, speaking before before Murray and Williams lost to the No 1 seeds.
'First, she is competing which is what she needed. Second, with Andy, they are feeding each other. They are two great champions and I think they exchange a lot of thoughts.
'And third she is enjoying her time on the tennis court. I think they are both having a lot of fun.'
Williams will take on unseeded Czech Barbora Strycova on Thursday afternoon for a place in her 11th Wimbledon final. After a sluggish start, in which she dropped a set to Czech teenager Kaja Juvan in the second round, she is now in menacing form.
'She started really slow,' said Mouratoglou. 'She was looking for her tennis. Her second round was a key moment because the first set she was really struggling. She dug deep and the next two sets were so much better.'
Despite Jo Konta's defeat by Strycova there will be some British interest in Thursday's semi-finals in the form of Andrew Bettles, the coach of No 8 seed Elina Svitolina.
The Ukrainian takes on Simona Halep in a match that looks too close to call and Bettles is delighted to be representing Britain in the coaching box.
'It's amazing, growing up Wimbledon was so special,' he said. 'To be here is amazing for me personally. I have to pinch myself.
'I wasn't a good enough player but the coaching side always fascinated me and Elina gave me the trust to be her main coach.'