Seven-time winner Serena Williams, who missed the tournament last year, faces Bulgarian qualifier Viktoriya Tomova.
Roger Federer and Serena Williams are both back on Centre Court at Wimbledon on Wednesday as they look to advance to the third round.
Play is under way on Day 3 at Wimbledon, with former finalist Milos Raonic of Canada among the early starters as the second round begins at the All England Club.
The 13th-seeded Raonic was playing John Millman of Australia as he bids to reach the third round for a sixth straight year. He lost the 2016 final to Andy Murray and reached the quarterfinals last year.
Number 10 Madison Keys of the United States was the highest-seeded woman in early action, playing Luksika Kumkhum of Thailand.
Federer will play Lukas Lacko of Slovakia as he continues his quest for a record-extending ninth title at the All England Club.
Williams then faces Bulgarian qualifier Viktoriya Tomova as she goes for a 16th straight match win at the tournament — having missed last year while pregnant.
Australian Open champion Caroline Wozniacki and last year's men's runner-up, Marin Cilic, are also back in action as they try to avoid more upsets at the tournament.
Three of the top-10 seeded men lost in the first round, while former champions Maria Sharapova and Petra Kvitova also went out on Tuesday.
The forecast calls for more sunny skies, although there is a 30 percent chance of rain showers in the afternoon.