MELBOURNE, Australia -- Madison Keys defeated one Williams sister Wednesday at the Australian Open. On Thursday, the 19-year-old American will try to make it two, and this sibling might be a little tougher, even with a cold.
Keys overcame a left thigh injury to beat No. 18-ranked Venus Williams 6-3, 4-6, 6-4 and advance to the last four against top-ranked and 18-time major winner Serena Williams, who had little trouble beating last year's finalist, Dominika Cibulkova, 6-2, 6-2.
In men's play, defending champion Stan Wawrinka beat Kei Nishikori 6-3, 6-4, 7-6 (6) to avenge a five-set loss to the Japanese star in the quarterfinals of the U.S. Open last year. Wawrinka, who let slip a 6-1 lead in the third-set tiebreaker and eventually needed six match points to close it out, will play the winner of the Novak Djokovic-Milos Raonic night match on Rod Laver Arena.
Serena Williams made her win look easy despite suffering from a bad cold the past few days. She spoke with a hoarse voice in her post-match interview on court.
"I have to keep my answers short because I keep coughing," Williams said.
"I've been sick the past few days, and it's just getting worse and worse, but hopefully it will get better," Williams added later. "I heard there's a virus going around with a lot of the players, and I think I caught it."
There had been some hope that the semis might feature an all-Williams matchup at a major for the first time in more than five years. The Williams sisters last met in a Grand Slam match at Wimbledon in 2009, when Serena won the final.
The semifinalists from the other half of the women's draw have already been determined -- No. 2 Maria Sharapova will play No. 10-seeded Ekaterina Makarova, also on Thursday.
Serena's win doesn't bode well for the other three women left -- all five past times Williams has advanced to the semifinals at Melbourne Park, she's won the tournament.
Venus Williams' loss ended an encouraging 10 days for the 34-year-old veteran at Melbourne Park. She hadn't advanced to the quarterfinals of a Grand Slam since the U.S. Open in 2010 and had struggled to recapture her earlier form after being diagnosed in 2011 with Sjogren's syndrome, an auto-immune disease that causes fatigue and joint pain.
But Williams is 9-1 to start the new year after capturing her season-opening tournament in Auckland, New Zealand, before the Australian Open.
"It already feels like a long season already, so many matches in a row," she said. "But it's a great start. Hopefully I'll be able to keep this level up."
Regardless of the quality of the match, in which the two players combined for 83 unforced errors, Keys was pleased to be through to the semis.
"It's amazing, you just have to embrace the moment," said Keys, who is now coached by three-time major winner Lindsay Davenport. "And I get to enjoy another moment next round."
She later identified her injury as a left adductor, and was optimistic it wouldn't affect her in her match against Serena. The same injury forced her to retire from her third-round match at Wimbledon last year.
"I think it's one of those things where all of us have dealt with injuries before," she said. "I'm probably going to have tape on it, but I'm just going to do my absolute best and enjoy the moment."
Wawrinka looked to be cruising in his tiebreaker with Nishikori, but the Japanese player saved match point after match point with a combination of great shots and errors by Wawrinka.
Nishikori made the biggest error at the wrong time, however, attempting a drop shot from the back of the court that bundled into the net. That set up another match point for Wawrinka, which he converted with an ace, his 20th of the match.
"Phew, I'm still nervous," Wawrinka said in his post-match interview on court. "It's never easy with his returning. You have to go for it."
Nishikori said he had a difficult day.
"I was struggling with my serve ... I couldn't get good rhythm in the first and second set," Nishikori said. "He played really aggressive, great tennis. Mentally I was fine, I was ready to go. But he was a little bit better today."
Andy Murray and Tomas Berdych will play in the other men's semifinal on Thursday.
