Venus Williams withstood a furious challenge from 21-year-old Greek qualifier Maria Sakkari, winning 7-5, 4-6, 6-3 to advance to the third round at Wimbledon on Thursday.
It was a banner day for Americans, with No. 18 seed Sloane Stephens handling Shuai Peng 7-6, 6-2 in her first-round match, which had been rescheduled during a rainy start to Wimbledon.
No. 9 seed Madison Keys is back in the third round for the third consecutive year, notching a 6-4, 4-6, 6-3 victory over Kirsten Flipkens.
In a stunning upset, second-seeded Garbine Muguruza of Spain was sent packing by Slovakian qualifier Jana Cepelova, who posted a 6-3, 6-2 victory. Cepelova easily dispatched the French Open champion by winning five of the first six games of both sets.
Third-seeded Agnieszka Radwanska of Poland fought off an upset bid to post a 6-2, 4-6, 9-7 victory over Croatia's Ana Konjuh. Fourth-seeded German Angelique Kerber rolled to a 6-1, 6-4 win over American Varvara Lepchenko.
American Coco Vandeweghe, seeded 27th, posted a 6-2, 6-3 win over Hungary's Timea Babos.
On the men's side, second-seeded Andy Murray sailed to a 6-3, 6-2, 6-1 victory over Taipei's Yen-Hsun Lu. Murray is 48-9 lifetime at the All England Club.
"If you can win matches easily it does help because you can rest," Murray said afterward. "It has been a good start. I will just try and do my best -- work hard, keep my head down and hopefully have a good tournament."
Murray next faces Australian John Millman, who recorded a 7-6 (5), 6-3, 4-6, 6-2 victory over 26th-seeded Benoit Paire of France.
Fifth-seeded Kei Nishikori of Japan advanced with a 4-6, 6-4, 6-4, 6-2 victory over France's Julien Benneteau and seventh-seeded Richard Gasquet of France moved on with a 4-6 7-5, 6-3, 6-1 win over Spain's Marcel Granollers.
Bulgaria's Grigor Dimitrov posted a 6-3, 7-6 (1), 4-6, 6-4 victory over Gilles Simon in a match that included an angry exchange between Simon and umpire John Blom.
Simon was angry that he had to play through a drizzle during the second set and the Frenchman was overheard saying, "If I play and get injured, I will sue you and you will pay."
In other matches, Jiri Vesely of the Czech Republic swept eighth-seeded Austrian Dominic Thiem 7-6 (4), 7-6 (5), 7-6 (3); Slovakian qualifier Lukas Lacko defeated 23rd-seeded Ivo Karlovic of Croatia 6-4, 7-6 (5) 6-2, and 18th-seeded American John Isner defeated Cyprus' Marcos Baghdatis 7-6 (2), 7-6 (5), 6-3.
Donald Young defeated Leonardo Mayer 6-4, 7-5, 3-6, 6-3 to advance to the second round.