Bertens dominated the world number three in the opening set, but
the 24-year-old became unwell early in the second set and was forced
to take a medical timeout.
She eventually retired with an illness in the final set to hand
Kerber a 1-6 6-2 3-0 win on another steamy day in south Florida.
"I think Kiki's a great player," Australian Open champion Kerber
said in her on-court interview.
"She played very well in the first set and I was not finding my
rhythm at the beginning.
"For me, it's not so easy. But I'm trying to focus on my game, doing
my stuff and not looking too much over the net.”
Up next for the German is unseeded Hungarian Timea Babos, who
advanced with a 7-5 6-0 win over Japanese wildcard Naomi Osaka.
Other third-round winners on Sunday included American Madison Keys,
Victoria Azarenka of Belarus, and Briton Johanna Konta.
[to top of second column]
Keys, the 22nd seed, upset ninth seeded 2015 U.S. Open finalist
Roberta Vinci of Italy 6-4 6-4.
(Reporting by Tim Wharnsby in Toronto; Editing by Andrew Both)
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