Former champion Agnieszka Radwanska stunned world No.1 Simona Halep as two former top-ranked players continued their resurgence at the Miami Open.
Radwanska, who won in Miami in 2012, claimed six of the last seven games to claim a 3-6 6-2 6-3 third-round victory after an hour and 48 minutes.
Two-time Grand Slam champion Kerber pushed past Anastasia Pavlyuchenkova in 6-4 6-4 while three-time Miami champion Victoria Azarenka needed three sets to get past Anastasija Sevastova of Latvia 3-6 6-4 6-1.
Halep, who was beaten by eventual champion Naomi Osaka in the Indian Wells semi-finals last week, took advantage of a woeful service game and 10 unforced errors by her opponent to take the first set.
But Radwanska, who only held her serve once in the opening set, dropped just four points in the opening four games of the second, breaking twice and opening up a 4-0 lead.
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Halep broke early in the third to lead 2-0 but unforced errors - 44 in total against 31 winners - proved too much for her to overcome and Radwanska emerged with the victory.
"I'm so happy, especially because she's been playing great tennis in the last couple of months," Radwanska told reporters.
The Pole's next opponent is Azarenka, whose ranking of 186 belies her ability.
"Those kind of matches are super important for me right now," Azarenka told reporters after her win.
Kerber, who went from world No.1 in July last year to No.21 by year-end, won more than two-thirds of her points on first serve and almost half of those on the racquet of her Russian opponent.
She faces Wang Yafan in the fourth-round after the Chinese qualifier knocked out local hope Alison Riske.
Fifth seed Karolina Pliskova also moved through after enduring a long battle with Taiwan's Hsieh Su-Wei in a 6-4 1-6 7-6 (7-4) win.
She'll face 24-year-old Kazakh Zarina Diyas, who broke the will of Carina Witthoeft in a 4-6 7-5 6-0 victory.
Garbine Muguruza beat Christina McHale to set up a showdown with Sloane Stephens, who reached the round of 16 after Romanian Monica Niculescu retired during the deciding set of their match.
America has three more hopes including Venus Williams on the other side of the draw, which also features Australians Ashleigh Barty and Daria Gavrilova.
