Former world number one Serena Williams believes that she has never been 100% physically fit.
After the match, the 13-times Grand Slam champion told reporters that she is working hard to improve her fitness ahead of the hard court season.
"I've been making a real effort to get fit and it is making a difference," said Williams.
"I just decided that if I could be fit, maybe that would bring a new level to my game.
"I have never been really fit. I'm still not super fit because I always have cream sodas at night!"
Williams will now face Victoria Azarenka for a place in the final.