Last year's runners-up were up first on the main show courts at Wimbledon Tuesday, and both came through in straight sets.
Angelique Kerber beat Irina Falconi of the United States, 6-4, 6-4 on Centre Court. On No. 1 Court, Milos Raonic defeated Jan-Lennard Struff of Germany, 7-6, 6-4, 7-6.
Novak Djokovic and Roger Federer advanced when their opponents had to retire in the second set.
Other first-round winners on the men's side include eighth seed Dominic Thiem and No. 10 Alexander Zverev, both in straight sets. Americans John Isner, Jack Sock and Ryan Harrison also advanced.
The highest men's seed to fall was No. 19 Feliciano Lopez, who had to retire in the fourth set of his match with Adrian Mannarino.
On the winner's side, Kerber is joined in the second round by third seed Karolina Pliskova, fifth seed Carolina Wozniacki, No. 7 Svetlana Kuznetsova and No. 9 Agnieszka Radwanska.
Wednesday's schedule features matches involving defending men's champion Andy Murray, two-time champ Rafael Nadal and Venus Williams.
