"It still hurts," she said of the left thigh strain that made her three-set defeat of Venus Williams - and progress to a first grand slam semi-final to give the Australian Open a third 19-year-old in the women's last four in as many years - so meritorious. "It's ... probably going to hurt [on Thursday]. I'm probably going to have tape on it, but I'm just going to do my absolute best and enjoy the moment."

Waiting to twist the dagger and render this new experience anything but fun is Serena Williams, herself battling a virus, while adding "familial vengeance" to her motivation in a first meeting with a rising star she and Venus have been asked about ad nauseum.

With the quarters and semis on consecutive days, Keys was preparing to virtually sleep on the treatment table. Up against it, she will doubtless fall back once more on what she knows best.

"At that point I knew I couldn't run as much," she said of the pain she felt early in the second set. "I knew if I was going to get stretched out it was going to be more painful. It was kind of that thing ... if you have it, go for it."

What Keys has is the biggest ball-striking game on the women's circuit, and one of the heaviest full stop. In her first-round match at last year's French Open - admittedly against the slow-hitting Sara Errani - Keys' groundstrokes were struck at an average of 123km/h. Novak Djokovic's ground balls in his first-round win over Joao Sousa averaged 122km/h. Here, Channel Seven has measured Keys' average wallop at almost 10km/h more than her peers.

On Wednesday she hammered 34 winners to Williams' 10. They spirited her away from a tentative beginning to a stretch of 20 points won of 24 played as she stormed to the first set and took the opening game of the second to love. And they shepherded her through an injury flashback she called "overwhelming .. kind of scary".

The same thigh muscle had tightened in the third round at Wimbledon last year. Then, she effectively closed her eyes and hoped it would go away. "I ignored it at Wimbledon, and, you know, tore it."

Now, panic set in, a desperation to get her leg strapped lest the same thing happen again. Trailing 1-4, she left the court for an injury time-out. In her box, coach Lindsay Davenport - whose notes include a 27-match catalogue detailing how tough it is to beat Venus Williams on two legs - shifted uncomfortably in her seat.

The three-time grand slam winner had cautioned her young charge not to become ruffled if her opponent got on top, to keep the pressure up, to stay calm. There was no contingency for how to beat her when barely able to get around the court.

"I think just being able to come back from being down and from not being able to move as well, not having as effective of a serve, just being able to kind of grind through that, still figure it out, manage to win some points, is what I'm most happy about," Keys reflected.

The sight of Williams on television inspired a four-year-old Keys to pick up a racquet - not her tennis but her dress. Now playing her last grand slam as a teenager, she admitted to drawing inspiration from Eugenie Bouchard and Sloane Stephens making the semis here before their 20th birthdays. Respect for the Williams sisters doesn't override a conviction that she now meets them as an equal.

"It's one of those things where you want to feel this way all the time," Keys said of breaking new ground. "But it's not, you know, this unbelievable excitement either 'cause you want to keep winning and you want to keep doing better. I am very happy and I am very excited, but also not getting too far ahead of myself and being too content where I am."

If only her leg can come to the party, Keys will tackle Serena Williams determined to live the words 34-year-old Venus offered in reflecting on an opportunity lost. "I think I'll just learn from this and come out stronger."