Coco Gauff lost six games in a row in a shock defeat by Katerina Siniakova at the Qatar Open.

Making her first appearance since losing to Aryna Sabalenka in the semi-finals of the Australian Open last month, Gauff was out of sorts and fell to a 6-2 6-4 defeat.

The American second seed looked to have turned things around after losing the opening set when she eased into a 4-0 lead in the second set.

But Czech Siniakova, better known for her achievements in the doubles game, responded with six games in a row for one of the biggest singles victories of her career.

Melbourne runner-up Zheng Qinwen, playing her first match as a top-10 player, came through 6-2 2-6 6-3 against Magda Linette, while teenager Linda Noskova, who was a quarter-finalist at the Australian Open, upset seventh seed Maria Sakkari 3-6 7-6 (2) 7-5.

Leylah Fernandez recovered from losing the first set to love to defeat Paula Badosa 0-6 6-2 6-3 and Victoria Azarenka was a 7-6 (2) 6-2 winner over Wang Xinyu.