In an entertaining conclusion, Kerber twice failed to serve out the match before finally completing a 6-3, 7-6(4) victory. The German will now face Elina Svitolina for a place in the quarterfinals.
"The match was on a really high level at the end of the second set. We run a lot, both of us. I think we both have a great return, so I think that was also the key from both of us to breaking back," Kerber said. "She breaks me back, and then I break her back.
"The games were still close. It was not like I lost my serve to zero or 15. There were still good points during my service games."