Naomi Osaka battled into the last 16 of the Qatar Open on Tuesday but Coco Gauff and Ons Jabeur crashed to surprise second-round exits with straight-sets defeats.

Four-time Grand Slam champion Osaka brushed past Croatia's Petra Martic 6-3, 7-6 (11-9), continuing a comeback from maternity leave after giving birth to her daughter in July.

Osaka grasped control with a break in the fourth game of the opening set. She broke twice more in the second set — on either side of dropping her own serve — only to blow a chance to close out the match at 5-4.