Key Biscayne, Fla. – In just four sets, Serena and Venus Williams moved one step closer Monday to a sister-sister semifinal showdown at the Sony Ericsson Open.

The potential match would mark the 16th meeting of the sisters and the third at the Sony Ericsson Open since the two met for the first time in 1998. Serena leads the all-time series 8-7.

 

“Playing Venus is like playing a mirror of me – she’s getting every ball back,” Serena said. “She has the hardest serve on the tour, she’s a great returner and she runs every ball down. She’s doing nothing bad, and it’s hard to play people like that.”

 

Venus advanced to the quarterfinals by winning her fourth-round match in two sets (6-3, 6-3) against 17-year-old Caroline Wozniacki.

 

“I think she’s progressing rapidly. I think she’s on the right track,” Venus said of her opponent. “She’s just trying to get stronger just like everyone else, and that’s the right thing to do: get stronger and play better.”

 

Venus’ strength was still too much for Wozniacki, as she was unable to return many of Williams’ power serves and only won six-of-29 points off of Venus’ first serve attempts.

 

Serena’s step toward Venus went strikingly similar, with the younger Williams defeating the Estonian Kaia Kanepi by the same score in two sets. Serena’s power also proved too much for Kanepi, who gave up nine aces in the match.

 

“She was a very interesting player,” Serena said. “She didn’t give me any kind of rhythm.”

 

Both sisters face major obstacles before reaching the semis, as Venus will play No. 3-seeded Svetlana Kuznetsova and Serena must face No. 1-seeded Justine Henin in Tuesday’s quarterfinals. Henin handily defeated Elena Vesnina and Kuznetsova beat Shahar Peer Monday to advance.

 

A great rivalry in its own right, Serena and Henin are 6-6 all-time against one another, with Serena defeating Henin in last year’s tournament final to secure her fourth Sony Ericsson Open Women’s Singles title.

 

“(Playing Serena) is a very good memory from last year, even if I lost the match. It was the day I understood that I could win against Serena,” said Henin, who went on to beat Serena in three different Grand Slam quarterfinal matches in 2007. “It doesn’t mean I am going to win tomorrow, but I think that that gave me a lot of confidence.”

 

“I think we have a great rivalry,” Serena said about playing Henin. “We definitely bring out some of the best tennis in each other and she tends to play really well against me, probably better against me than other opponents. So it’s definitely a good match for me.”

But all potential matchups at this year’s Sony Ericsson Open pale in comparison to the Williams’ sibling rivalry. With 845 combined singles tour wins and 14 Grand Slam titles on the Williams’ mantelpiece in Palm Beach Gardens, Fla., the sisters stand to collide with atomic force in the semis.

 

“Do I like playing Venus? Of course not,” Serena said. “I think she’s the toughest opponent out there for me.”