Karolina Pliskova kept her Brisbane International title defense on track with a 3-6, 7-5, 6-2 win over 2012 winner Kaia Kanepi to set up a semifinal against Elina Svitolina. Pliskova opened last season with victory in Brisbane and rose to the No. 1 ranking in July before finishing 2017 at No. 4. She struggled against Kanepi's powerful ground strokes in the first set but started to find rhythm in the second to level the match and was dominant in the third.
Svitolina secured her semifinal spot when Johanna Konta retired with a hip injury in the third set of their quarterfinal.
The third-seeded Svitolina won with a score of 1-6, 7-6 (6), 3-2, retired, having just held serve when Konta walked to the net and said she could no longer continue, two games after receiving treatment for a right hip problem.
Konta's exit came two days after No. 2-ranked Garbine Muguruza retired in the third set of her first match of the season after struggling with leg cramps.
Konta was unsure if she'd be fit enough to attempt a defense of her Sydney International title next week or what it would mean for her chances at the Australian Open, where she reached the semifinals in 2016 and the quarterfinals last year.
"I only know kind of the initial feelings of it, which is not always so trustworthy," she said of the injury. "So I don't feel too comfortable saying really too much.
"Hopefully it's nothing more than a low-grade strain and more muscle spasm."
Seventh-seeded Anastasija Sevastova beat Aleksandra Krunic 6-2, 6-4 to move into a semifinal against qualifier Aliaksandra Sasnovich, a 3-6, 6-2, 6-3 winner over Alize Cornet.
Denis Istomin and Ryan Harrison will meet in the quarterfinals in the men's draw. Istomin advanced 7-6 (5), 6-2 over Jared Donaldson and Harrison had a 6-7 (5), 6-4, 6-2 win over Yannick Hanfmann, who was a late addition to the draw after Andy Murray withdrew.
Kyle Edmund had a 7-6 (3), 5-7, 6-4 win over Chung Hyeon and will next play the winner of the night match between defending champion Grigor Dimitrov and John Millman.
