Ex-world number one Angelique Kerber came back from a set down to beat Britain’s Johanna Konta 1-6 6-1 6-3 and reach the Qatar Open quarter-finals.

Tenth seed Konta, 26, raced into a 5-0 lead against the eighth seed and won the opening set in 37 minutes.

But the 30-year-old German took the next in 28 minutes and secured an edgy decider in Doha.

She will play world number one Caroline Wozniacki in the last eight after the top seed beat Monica Niculescu 7-5 6-1.

Kerber won the Sydney International last month and reached the Australian Open semi-finals where she was beaten by Simona Halep.

Having lost her most recent meeting with Konta on the grass at Eastbourne last summer, Kerber could not contain the world number 11 in the early exchanges and the Briton went ahead with her sixth set point.

However, world number nine Kerber soon took command, wrapping up the match in one hour 51 minutes and maintaining an unbeaten record in three matches on hard court against Konta.

Wozniacki committed 18 unforced errors against the unorthodox world number 92 Niculescu and complained to French umpire Emmanuel Joseph during the match about the Romanian’s grunting.

“It isn’t in the rule book that you are not allowed to grunt when the opposing player hits?” the 27-year-old Dane asked.

In a courtside interview after her victory in one hour 30 minutes, Wozniacki said of 30-year-old Niculescu, who beat Maria Sharapova in the first round, “she tries to get in your head.”

Defending champion beaten by teenage qualifier

Elsewhere, unseeded 18-year-old American qualifier Catherine Bellis beat defending champion and fifth seed Karolina Pliskova 7-6 (7-4) 6-3 in an hour and 36 minutes.

The world number 48 broke Pliskova’s powerful serve five times and it was the teenager’s first success against a player in the world’s top five.

She attributed part of her success down to eating ice cream every night in Doha, which “gives me a bit of energy”.

Bellis will play second seed Halep in the quarter-finals after the Romanian saw off Anastasija Sevastova of Latvia 6-4 6-3.

Third seed Elina Svitolina of Ukraine was beaten 6-4 7-5 by former Wimbledon champion Petra Kvitova, seeded 16.

Left-hander Kvitova, 27, has won her past seven meetings with Svitolina and since a first-round defeat to Andrea Petkovic at the Australian Open, the Czech has now won 10 consecutive matches.

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