World No.1 Simona Halep overcame a sluggish start to beat Wang Qiang in the fourth round at the WTA tournament at Indian Wells.
The 7-5 6-1 victory booked a quarter-final against Petra Martic in the California desert.
The turning point came after a string of unforced errors left Halep trailing 5-4 in the first set, prompting her Australian coach Darren Cahill to tell the defensive specialist to work longer points and reduce the error count.
Halep went on to lose only one more game, easily seeing off the challenge of the world No.55 from China.
The 26-year-old Romanian showed no sign of the foot injury that forced her to withdraw from the Qatar Open last month and is well positioned to make a run at reclaiming the Indian Wells title she won in 2015.
First she will have to get past unseeded Croatian Martic, who advanced to the last eight with a 6-3 7-6 (7-4) win over Marketa Vondrousova.
“She is a very tough opponent because she is serving pretty strong and also the forehand has a lot of top spin … So I will have to work hard,” Halep told the Tennis Channel.
Halep needs to reach the final at the Tennis Garden to retain her place at the top of the WTA rankings from Dane Caroline Wozniacki.
Former world No.1 Karolina Pliskova used her powerful serve to overwhelm 16-year-old Amanda Anisimova and advance to the last eight for the third year in a row.
Pliskova’s 6-1 7-6 (7-2) victory ended a remarkable run for the young American, a tournament wildcard who took out ninth-seeded Petra Kvitova in the third round for the biggest win of her young career.
Pliskova will play Japan’s Naomi Osaka after her 6-1 5-7 6-1 win over Greece’s Maria Sakkari.