Iga Swiatek started her clay season with a straight-sets victory over Elise Mertens at the Stuttgart Open.
The world No. 1 was not at her ruthless best and was given a good test by Mertens, but she prevailed 6-3 6-4.
“I just wanted to play with as much intensity as I can and get used to the court,” said Swiatek, who will next play either Emma Raducanu or Linda Noskova.
Ons Jabeur’s search for her best form continued as she was beaten by Jasmine Paolini in the last 16.
The world No. 9 has only won three of 10 matches this season and lost 7-6(8) 6-4 to Paolini, who next faces fourth seed Elena Rybakina.
Rybakina earlier recovered from a second-set wobble to beat Veronika Kudermetova 7-6(3) 1-6 6-4 and book her spot in the last eight.
Swiatek overcomes Mertens opener
Having been playing on hard courts at the Billie Jean King Cup last weekend, Swiatek did not take long to find her feet on her favourite surface as she opened up a 3-0 lead.
Mertens responded in the next game as she crushed a return winner to get one break back.
Swiatek then seemed to lose her way slightly as Mertens won 11 of 15 points. But from 0-30 down at 5-3, Swiatek won four points in a row to take the set.
However, she fell 0-40 behind in the next game and although she rallied to deuce, she was broken at the fourth attempt by Mertens.
A tight finish looked in store until Swiatek broke to love in the seventh game.
Mertens produced an incredible defensive effort to save a match point as Swiatek looked to close out the win.
But she could not return a drilled backhand winner or a cross-court forehand as Swiatek sealed the win in style.
Jabeur misses set points in Paolini loss
She had two set points in the tie-break but Paolini narrowly saved the first with a shot that the umpire came down to check and ruled had just caught the line.
Paolini brought up her own set point with a forehand winner and took it when Jabeur hit the top of the net and the ball went out.
Both players shared a break early in the second and had plenty of chances throughout, but once again it was Paolini who was more clinical.
After saving two break points in the eighth game, Paolini broke to lead 5-4.
She then fended off two more break points as she served out the win to reach the next round.
Rybakina battles through to quarter-finals
Rybakina was forced to dig deep in a marathon contest that lasted more than two-and-a-half hours.
The pair traded blows early in a tight opening set but Kudermetova was made to pay for failing to take three chances to break at 5-5.
She forced a tie-break and led 2-1 before Rybakina reeled off six of the next seven points to claim a one-set advantage.
Kudermetova responded emphatically by racing into a 5-0 lead and taking the contest all the way to a decider.
She then recovered from 4-1 down in the third set to level at 4-4 but Rybakina would not be denied, holding to move 5-4 ahead before breaking to seal a hard-fought victory that saw her progress into her seventh quarter-final of the season.