The 24th seed Muguruza, who stunned Williams in the second round at Roland Garros last year, threatened another upset as she tore through the first set with a barrage of sweetly-struck winners on a cool, windy day.
“Someone in the crowd said ‘come on Serena, use spin,'” Williams said in a courtside interview. “There are coaches everywhere here.”
Williams later told reporters the advice had hit home. “I was like, ‘you’re right. I’m trying to do that anyway, but I wasn’t doing it’.
“It’s been really great. I hear my name throughout the whole stadium like 360 (degrees). I don’t get that everywhere. It feels good.”