Coco Gauff lost the first set in 20 minutes but roared back to stun seventh seed Elise Mertens – as Iga Swiatek also staged a comeback at the Viking International in Eastbourne.

Playing late in the day, Gauff was picked apart by Mertens to begin with, and also trailed by a break in the second set, but the 17-year-old American rising star pulled off a 0-6 7-6 (7-4) 7-5 first-round win.

Seeds Elina Svitolina, Bianca Andreescu and Swiatek all came through three-set matches on a busy day, but Karolina Pliskova was not so fortunate in her opener.

Winner of the grass-court event in 2017 and 2019, Pliskova arrived as the defending champion after last year's edition was cancelled amid the coronavirus pandemic.

However, her hopes of a repeat triumph came to an early end, beaten in three sets by qualifier Camila Giorgi.

The fifth seed was in charge initially against an opponent she had prevailed against in five of their six previous meetings, yet Giorgi produced an impressive response having fallen behind – aided by a strong service performance – to win 2-6 6-2 6-2.

Svitolina, the second seed, had lost in her previous two appearances in the main draw, and it appeared history could be repeated when Paula Badosa claimed the opening set against her.

Yet the second seed recovered to level, then dominated the tie-break in the decider to triumph 4-6 6-1 7-6 (7-1) and set up a second-round meeting with Elena Rybakina, who edged out wildcard Harriet Dart in three sets.

Andreescu, meanwhile, recorded her maiden win on grass in the main draw of a WTA tournament. The Canadian was made to work for it by Christina McHale, eventually coming out on top by a 6-4 2-6 6-2 scoreline.

Swiatek eventually saw off the challenge of Heather Watson after two hours and 42 minutes on court, a 6-3 6-7 (4-7) 7-5 triumph making sure of a place in the last 16. Watson led 4-1 and 40-0 in the decider but could not finish off last year's French Open champion.

This year's Roland Garros runner-up, Anastasia Pavlyuchenkova, meanwhile, was beaten 6-1 6-3 by Jelena Ostapenko.

At the Bad Homburg Open, second seed Victoria Azarenka defeated fellow Belarusian Yuliya Hatouka 7-5 6-0 to reach the last 16.

Jessica Pegula bowed out, though, as the American – seeded third – went down in a three-set tussle against Katerina Siniakova.

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.