Kvitova makes it eight in a row

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After Maria Sharapova was an early casualty at the Qatar Open, normal service was resumed on a good day for the seeds in Doha.

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The renewal of Garbine Muguruza's coaching relationship with Conchita Martinez got off to a strong start as she defeated Duan Ying-Ying.

Having been in her corner during Muguruza's Wimbledon triumph last year when regular coach Sam Sumyk was absent as his wife was expecting their first child, Martinez is back in the Spaniard's team as she tries to revive her fortunes after a disappointing 2018 to date.

Muguruza lost to Hsieh Su-wei in the second round of the Australian Open, but a shock was never on the cards against Duan, the two-time grand slam champion winning 6-3 6-4 to reach the third round.

She needed eight match points to seal the win and said afterwards: "It was a very tough match. It doesn't matter how many match points I had, I won! That's the important part, and I'm so happy because it's been so long since I've competed. It's good to have a victory."

Muguruza will face either Elise Mertens or Sorana Cirstea in the next round. Mertens beat Timea Babos in three sets while Cirstea overcame Maria Sakkari.

Petra Kvitova extended a hugely impressive winning streak, while the likes of Caroline Garcia, Johanna Konta and Madison Keys were in fine form as they all kept alive their hopes of winning the WTA Premier 5 tournament.