MALLORCA, Spain - No.7 seed Lucie Safarova and No.1 seed Caroline Garcia had been dealt two of the toughest first-round draws at the Mallorca Open - but both favorites came through tight matches to fight another day.

Safarova, playing her third tournament back after a three-month spell on the sidelines due to illness, was up against wildcard Marta Kostyuk, the 15-year-old who has raised her ranking nearly 400 places since January - and came through 6-4, 7-5, coming from a break down in the second set to reel the prodigy in.

In a match of few extended rallies, both players sought to impose first-strike tennis on each other - and although the Ukrainian showcased a formidable first serve, hammering down eight aces, she also negated this advantage with 11 double faults and just a 56% first serve percentage.

Safarova, by contrast, was not only steadier behind her delivery but in far greater control off the ground, striking smooth winners on big points - such as the forehand down the line with which the first set was sealed. Kostyuk, playing only her fourth professional match on grass, was frequently caught out by the unusual bounce, and as the second set slipped from her grasp from 4-1 up, the depth of Safarova's returns would reliably elicit errant backhands from the World No.136.

Top-seeded Garcia was also made to work hard as the crafty, in-form Hsieh Su-Wei kept her battling for two hours and 11 minutes before falling 7-6(4), 1-6, 6-4 in an enthralling stylistic contrast. The Frenchwoman led throughout the first and third sets, but the World No.52's unique, self-described "Su-Wei style" kept pegging her back.

Hsieh would save four set points in the first set before Garcia eventually came through the tiebreak; undeterred, and starting to read the Wuhan and Beijing champion's serve better, the 32-year-old dazzled to dominate the second set, allowing her opponent just 12 points in total.

Twice in the decider, Garcia powered to a break lead - and twice Hsieh hauled her back. However, the Chinese Taipei No.1's own serve had been vulnerable throughout the match - and staring down a third match point, a seventh double fault ended her valiant play. Garcia will face qualifier Johanna Larsson in the second round, as the Swede came from a set down to beat Sorana Cirstea 2-6, 6-3, 6-2.

Elsewhere, qualifier Rebecca Peterson scored the first upset of the day, stunning No.8 seed Danielle Collins 6-3, 6-3. The American is the fourth seeded player to lose in the first round in Mallorca this year following the upsets of No.4 Anett Kontaveit, No.5 Carla Suárez Navarro and No.7 Aryna Sabalenka yesterday.

Conversely, five out of six qualifiers have made it through their opening main draw matches. Alongside the Swedish duo are Ajla Tomljanovic, who struck five aces in beating Magda Linette 6-3, 6-4; Sofia Kenin, scoring her first Tour main draw win on grass 6-3, 3-6, 6-3 over Kateryna Kozlova; and Antonia Lottner, backing up her quarterfinal run in 's-Hertogenbosch last week by routing Aliaksandra Sasnovich in just 59 minutes. The sixth and final qualifier, Alison Riske, is due to play No.2 seed Angelique Kerber later on Tuesday.