By Steve Gorten

KEY BISCAYNE – The women’s semifinals at the 2015 Miami Open are set, and one of the two matches features the world’s No. 1 and No. 3 players, Serena Williams and Simona Halep, going head-to-head.

After Williams beat Sabine Lisicki in three sets during the day session Wednesday, the third-seeded Halep advanced with a 6-1, 7-5 win against unseeded Sloane Stephens in the first match of the night session.

“I’m really happy I played like this. It was an amazing match for,” Halep said. “I played my best until 3‑0 in the second set and then I lost my rhythm a little bit. She changed tactics and it was more difficult for me to hit the ball. But I’m really happy that I could finish in two sets and to stay focused until the end.”

The 23-year-old Romanian raced out to a 6-1, 3-0 lead in about 40 minutes. But Stephens, born and raised about a 40-minute drive north of Crandon Park Tennis Center, wouldn’t go down easily.

The 22-year-old American, the youngest player to advance to the quarterfinals, and the fifth unseeded women’s player to do so since 2008, captured five of the next six games before Halep closed out the match by winning the final three games.

“I got off to a slow start,” Stephens said. “Playing the No. 3 player in the world is always going to be tough, so I was just happy that at the middle of the second set I was able to come back and fight really hard and make her play a lot of balls.”

“She just played really hard the whole way,” Stephens added. “Unfortunately, I didn’t come up with some shots that I wanted to. But it was what it was.”

Halep has a chance to join Steffi Graf (1994, 1996) and Kim Clijsters (2005) as the only players to win Indian Wells and the Miami Open in the same year. If she wins the Miami Open, she would also overtake Maria Sharapova for No. 2 in the WTA world rankings. Sharapova lost her opening match here to fellow Russian Daria Gavrilova.

Halep and Williams were scheduled to face off in the semifinals at Indian Wells, but Williams withdrew because of a knee injury. Her knee hasn’t been an issue at the Miami Open, where she’s now won 16 consecutive matches dating back to 2012.

Williams said Wednesday she looked forward to her matchup against Halep after it didn’t happen last month.

“I was really disappointed to not be able to play and just not even be close to 100 percent,” Williams said.

Williams has won four of their five matchups, though Halep’s win – 6-0, 6-2 during the round robin portion of last year’s BNP Paribas WTA Finals in Singapore – equaled the worst loss of Williams’ career in regard to total games won. The two met again in the finals of that tournament and Williams won 6-3, 6-0.

“I expect a really tough match because she’s the best player in the world. She has a lot of experience,” Halep said, adding that her confidence is “very high” heading into this matchup. “I have to play aggressive like I did today at the beginning the match. This is the most important thing to have a chance against Serena.”

Ninth-seeded Andrea Petkovic will face 12th-seeded Carla Suarez Navarro in the other semifinal.