Top seed Garbine Muguruza made hard work of beating qualifier Magda Linette to set up a Wuhan Open quarter-final against Jelena Ostapenko.
The world number one bossed the first set, but the 82-ranked Linette dominated the second and offered resistance in the third before the Spaniard won 6-2 1-6 6-4.
Muguruza, under pressure from Karolina Pliskova to retain top spot in the rankings, was broken four times but battled her way into the last eight on Wednesday.
The Wimbledon champion looked set for a routine victory as she dominated the first set with clean hitting, not appearing to be hampered despite playing with a strapped left thigh.
Muguruza, who required treatment to that leg during a straight-sets win over Lesia Tsurenko on Tuesday, was very much second best in the second set as Polish outsider Linette hit back.
Linette went a break up at 2-0 when Muguruza fired a forehand into the tramlines and raced into a 5-0 lead before a short delay due to rain.
Staff frantically attempted to dry the courts with towels and Linette wrapped up the set following the resumption, with Muguruza getting herself out of trouble by saving three break points in the first game of the decider.
There were five consecutive breaks in a tense final set, the last of which came when Linette drilled a forehand long to ensure Muguruza will play Ostapenko in a battle of two reigning grand slam champions.