Venus Williams overcame sixth seed Agnieszka Radwanska at the Australian Open to reach her first Grand Slam quarter-final since 2010.
The 34-year-old American, who suffers from Sjogren’s syndrome, a disease that can cause fatigue, won 6-3 2-6 6-1.
The seven-time Grand Slam champion will face teenager and fellow American Madison Keys in the last eight.
Venus will play sister Serena, who beat Garbine Muguruza 2-6 6-3 6-2, in the semi-finals, if they both win again.
Venus was pushed hard, too, losing the second set as her level dropped before regrouping and upping the power to clinch the decider.
Asked what had inspired her successful run in Melbourne, Venus said: “Definitely my sister Serena, she’s just the ultimate champion.
“And definitely a lot of inspiration from all my fans who have stayed behind me through thick and thin.”
Venus, whose best performance at the Australian Open is a runner-up finish in 2003, last reached the quarter-finals of a Grand Slam at the US Open in 2010.
Keys is relishing the prospect of facing one of her childhood heroes.
“I’m just really excited. It’s a huge opportunity for me,” she said.
“I think Venus has helped the sport, especially the women’s side with equal prize money. She was a huge part of that. Just watching her is inspirational.
“She’s had her health battles but she loves tennis. She’s still out there and she’s doing it remarkably well. I hope I can be someone similar to that.” (bbc sport)