Her opponent Muguruza said she wasn't sure what to expect from Clijsters but her second set performance was impressive.
"I'm sure she's going to get better and better, for sure give us a lot of trouble," she added.
Last year the four-time grand slam champ announced she was coming out of retirement at the age of 36 to play in the WTA Tour in 2020.
“Hi guys, I’m excited to finally be able to share this news with you …” she captioned a clip of herself. Then, on camera she explained: “For the past seven years I’ve been a full-time mum, and I love it. I really, really do. But I also loved being a professional tennis player. And honestly … I miss that feeling.”
“So… what if I tried to do both? Could I be a loving mum to my three kids and be the best tennis player I can possibly be?”
“Let’s do this, let’s come back one more time,” she added. “See you in 2020.”
As she alluded to in the video, this marks the Belgian's second comeback to the sport. She first quit the game citing debilitating injuries just two years after taking out top spot at the 2005 US Open. In 2009 she was back on the court and went on to claim her second and third win at the tournament, as well as the Australian Open. Then, after 41 WTA titles and a 20-week stint as the world no.1, she hung up her racket once more.
Speaking on the WTA Insider podcast, Kim said her decision to return to the game has been in the works for a while.
“I don’t really feel like I want to prove something,” she said. “I think for me it’s the challenge.”
“The love for the sport is obviously still there. But the question is, am I capable of bringing it to a level where I would like it to be before I play at a high level of one of the best women’s sports in the world.”
“I want to challenge myself and I want to be strong again. This is my marathon.”