Date-Krumm, who at age 43 this year became the oldest woman in the Open Era to reach Wimbledon's fourth round, ousted seventh-seeded Laura Robson 6-4, 6-4 with two breaks in each set.
Date-Krumm saved five of the seven break chances Robson had and took nearly half of the points (31-of-65) when receiving serve.
Vania King, inserted into the draw when Jelena Jankovic withdrew, notched a bigger upset win in eliminating fourth-seeded Flavia Pennetta 3-6, 7-5, 6-0. Pennetta had 12 aces but also eight double faults. That contributed to King having 23 break opportunities.
King dominated the third set, losing just nine points and finishing off three of her six break chances to advance.
No. 2-seeded Sabine Lisicki needed 1 hour, 44 minutes to get past Chanelle Scheepers 7-5, 7-6 (7-1) while sixth-seeded Madison Keys had a much easier time in a 6-3, 6-2 win over Anna Schmiedlova. Also, ninth-seeded Kristina Mladenovic played for nearly 2 hours before beating Aleksandra Wozniak 7-6 (7-4), 6-4.
Swim Week Miami Beach 2014 [PHOTOS]