Naomi Osaka stumbled badly in her first match since winning the Australian Open as the world No 1 went down in a flurry of errors to exit the Dubai Championships on Tuesday.
Dubai-based Frenchwoman Kristina Mladenovic claimed a 6-3, 6-3 victory to reach the third round as Osaka made 25 unforced errors.
The rout, which featured seven breaks of the Osaka serve, took barely an hour, sending Mladenovic into a Wednesday contest with Carla Suarez Navarro.
"This is my home tournament, I live here," world No 67 Mladenovic said. "It's great to get a win like this in front of a big crowd. Beating the No 1 is always special."
The second set was riddled with seven consecutive breaks of serve before Mladenovic finished off the job with a winner to the empty court on match point.
Osaka stunned the tennis world last week by announcing her split from coach Sascha Bajin despite winning back-to-back Grand Slam titles at the US Open and Australian Open.
She said earlier this week that she would not prioritise "success over happiness" when asked about the sacking, and she never looked like winning in Dubai as she also served five double faults.
