Petra Kvitova came from a set down to beat Katarzyna Piter on her return from injury at the Bad Homburg Open, while no play was possible in Eastbourne on Monday due to rain.
Kvitova withdrew from the French Open after suffering a freak ankle injury during her post-match media duties at Roland Garros.
The two-time Wimbledon champion recovered to get her grass-court season under way in Germany and battled to a 4-6 6-1 6-4 over Polish outsider Piter.
A week before the third grand slam of the year gets started at the All England Club, top seed Kvitova trailed 2-0 in the final set as she struggled with her serve, but broke three times to book a second-round meeting with Ann Li.
Sloane Stephens withdrew ahead of her scheduled match with Laura Siegemund due to a foot injury. Riya Bhatia stepped in with Stephens absent, but Siegemund consigned her to a 2-6 7-6 (7-1) 6-1 defeat.
Angelique Kerber needed only 50 minutes to see the back of Ekaterina Yashina 6-1 6-1 on home soil, grasping all five break-point opportunities.
Kerber will do battle with Anna Blinkova in round two and Jessie Pegula's next assignment is an encounter with Katerina Siniakova following a 6-1 6-2 defeat of Amandine Hesse.
Blinkova beat Clara Tauson 7-6 (7-4) 4-6 6-2, while Sara Sorribes Tormo saw off Martina Trevisan 6-4 3-6 6-2
Miserable weather in Eastbourne prevented Karolina Pliskova, Madison Keys, Bianca Andreescu and Madison Keys from playing at the Viking International.