Madison Keys overcomes injury, Venus Williams to make semis

The 19-year-old took the first set in 29 minutes but suffered an injury to her left thigh in the second, which affected her movement and allowed her American compatriot to seize a 4-1 lead following a double break.

Keys took a medical time-out after that game and returned with strapping around her leg and somehow broke Williams twice to get it back on serve, but was then broken again and Williams served out the set 6-4.

In the decider, Williams earned a double break and was serving to take a 5-3 lead but teen sensation Keys broke for the second time to level it at 4-4.

The emerging American talent then broke again in the final game to clinch the match and set up a semi-final against Venus' sister Serena.

"It was definitely kind of a flashback to Wimbledon for me," she said of her injury scare midway through the match.

"I have had some problems with that part of my leg. It was kind of scary but luckily I was able to catch it before I did any real damage to it."

Of the victory, Keys added: "It was kind of an overwhelming moment."

Following her elimination from the tournament, Venus claimed that Keys' injury time-out had cost her the momentum.

"I felt like I really got off rhythm after that break. It was hard to come back," the 34-year-old told reporters.

"Never really felt like I got back to that rhythm that I was building at 4-1 and really just started to feel good about everything.

"I think for her, when you're injured, you feel a little tentative at the beginning. After a while you feel okay and so then you start to be more relaxed."

Williams' quarter-final appearance was her best performance at a grand slam since the semi-finals of the 2010 U.S. Open and continued her outstanding start to the season after beating Caroline Wozniacki to win the Auckland title.

Her ranking will improve to just outside the top 10 when the new standings come out, an impressive return after her struggles in recent years with Sjogren's syndrome, an auto-immune disease that can cause chronic fatigue and joint pain.

"It's definitely been a great last four weeks, I think," Williams said.

"A lot of match wins, a lot of momentum, just a lot of great things happening that everybody wants to happen in their career.

"I think a lot of players would have been happy with this tournament. I'm happy with progress. I'm not happy with a loss, I'll tell you that."