The No.23-seeded Lisicki rebounded big time after dropping the first set to the No.14-seeded Stosur, hitting 24 winners to just five unforced errors across the second and third sets to win, 46 62 61.
"Sam played a fantastic match," Lisicki commented. "I think going through that challenge makes me feel ready for the next one, as well. There are always things to improve, but I felt great out there."
"I played a great first set - couldn't have been happier with the way that set went - then it was just a couple points here and there," Stosur said. "I gave myself lots of chances but just couldn't get one of them. I would have loved to win, but I have to be happy with the way I played out there overall.
"So as disappointing as it is, this is probably the best I've felt walking away from Wimbledon."
"It's my favorite tournament," Lisicki said. "I love playing here at Wimbledon. Centre Court is something so special to play on. It's really fun to be here in the second week for the fourth time in a row.
Up next for Lisicki is the No.1-ranked, No.1-seeded Williams, who beat Japanese veteran Kimiko Date-Krumm, 62 60. It was a special match for Williams - under the lights, under the Centre Court roof.
"It was definitely special," Williams said. "I prefer this one because it's indoor and it's grass. I missed all those indoor carpet tournaments in the '90s that I should have played, and I didn't know that that was really good for my game. Yeah, playing indoors on grass for me is like amazing, for sure."
Exactly why is it amazing? "I love the atmosphere," Williams explained. "I love the sound the ball makes. You really hear the sound. I feel like the crowd is louder. It just feels really cool."
And what are Williams' thoughts about hitting 600? "I thought I just got to 500 wins," she said when told of the milestone at her press conference. "That's the first thing that comes to mind. Wasn't it not that long ago? I feel like it just happened, so I'm a little shocked they told me I had 600 today!"
Williams was asked which one of the 600 wins is the most special. "I have to say Australia, 2003," she commented. "It's four in a row, four Grand Slams in a row. That has to be the best one."
Date-Krumm was impressed with the World No.1. "She is the strongest women's player," she said. "She has a very good serve. Normally I have a good return, but her serve is too good, so it was very difficult to return well. And when I hit even my fastest serve, she hits down the line. It's a very difficult situation. She has so much power and so much speed. She has everything. It wasn't easy.
"But I tried my best. I had some good points. I just think she's very, very special."
"I honestly never thought I would play until my 30s, to be honest, though I don't see myself stopping anytime soon," Williams said. "However, I don't see myself playing into my 40s. That's why I have so much respect for Kimiko. She's playing so well, she's so fit and so good. So much respect for her."
Williams has beaten Lisicki in both of their previous meetings, though one was via retirement.
"I fell like she's serving massive," Williams said. "I feel like she plays some of her best tennis on grass. She always pulls an upset. It will be a really tough match. I have to get really serious for this one."
"You have to play your best to beat her, but everybody's a human being, so we'll see what happens," Lisicki said. "I don't know. I was in this situation last year when everybody was saying Sharapova was the favorite. I'm probably going into this match being the underdog too, but I like it like that.
"I have nothing to lose."