Top seed Simona Halep battled past German Julia Goerges 7-6(1), 7-6(6) in the last-eight clash of the Qatar Open on Thursday to set up a semi-final match against Ukrainian Elina Svitolina.
Playing in her first tournament with new coach Thierry Van Cleemput, Halep raced to a 4-0 lead in the opening set before her ninth-seeded opponent fought back to force a tiebreak.
Goerges threatened with an early break in the second set but Halep`s relentless accuracy from the baseline proved the difference as the Romanian closed out the win in just over two hours.
Fourth seed Svitolina swept aside Czech qualifier Karolina Muchova 6-4, 6-2 to move into her first semi-final of the season.
Svitolina broke her opponent twice in each set, winning 78 percent of points on her first serve in a commanding display.
Muchova, who has enjoyed a breakthrough week to reach her first WTA quarter-final, was undone by her 25 unforced errors, allowing Svitolina to clinch an 82-minute victory.
"She`s (Muchova) not as a typical young player, because most of the players now that are coming up, they are smashing the ball," Svitolina said.
"She has lots of variety in her game, and that`s, I think, very good for tennis," she added.
Three-time Grand Slam winner Angelique Kerber rallied from a set down to overcome Czech Barbora Strycova 1-6, 6-2, 7-6(4), reaching her first semi-final since her Wimbledon triumph in July.
Kerber`s Australian Open campaign in January ended in one of the worst defeats of her career when she won only two games against Danielle Collins, but she has put her disappointment behind her by stepping up her game in Doha this week.
Both players converted five break points each in a riveting contest but it was Kerber who kept her composure in the decisive tiebreak to improve her head-to-head record to 8-1 against Strycova.
"We played so many times against each other," Kerber told reporters.
"You never know what to expect, if she is playing serve and volley or just moving, playing fast. It was a really close match, and I think just one, two points decide the match," Kerber added.