DOHA (AFP) - Simona Halep shrugged off injury concerns to record a straight sets victory over Anastasija Sevastova on Thursday (Feb 15) to progress to the Qatar Open quarter-finals.

The world number two won 6-4, 6-3, hit 29 winners and needed four match points before overcoming her Latvian opponent, who is ranked 15th in the world.

Coming into the match, Halep admitted she had lingering concerns about an ankle injury which had kept her out of action since her defeat to Caroline Wozniacki in the Australian Open final last month.

But she seemed relatively untroubled breaking her opponent's serve late in each set to advance to the last eight.

"I'm really glad that I could finish it in two sets and play like I played," said Halep. "I mean I'm really pleased with the way I played today and very confident."

She added that her ankle was painful but had not got worse during the match.

"Day-by-day I will see how it is and then I will decide if something is getting worse."

Defending champion and world number three Karolina Pliskova though is out.

She was beaten by American qualifier Catherine Bellis, 6-7 (4/7,) 3-6, the first time the teenager has beaten someone in the top five.

"I think it's definitely a milestone. It's great," said the 18-year-old.

Her victory also ensured that for the fifth consecutive year, the Qatar title will not be retained by the defending champion.

World number four Garbine Muguruza breezed through her match against Romania's Sorana Cirstea, winning 6-0, 6-4.

"I'm very happy with the performance. I'm looking to play as many matches as I can. So it's good.

All of the world's top five are in action on Thursday, though the most anticipated clash is that between world number nine Angelique Kerber and the woman ranked just two places below her, Britain's Johanna Konta - the last match on centre court.