Benoit Paire was gifted a place in the second round at the Hamburg European Open by Ricardas Berankis' foot injury, but fellow countryman Richard Gasquet could not get past Marco Cecchinato in his first-round clash in Sweden.
Lithuania's Berankis forced Paire to a first-set tiebreak but, due to rolling his ankle earlier in the game, then had no option but to retire hurt.
His retirement granted Paire just his third ATP win of 2021.
At the same event, there was also a first ever ATP win for Sebastian Baez, who coasted past Corentin Moutet 6-1 6-2 to claim a straight-sets victory.
In the Nordea Open, held in Bastad, Italian Cecchinato triumphed over former world number seven Gasquet 6-2 5-7 6-3 to reach the second round.
The 2018 Roland Garros semi-finalist, who fought off Gasquet's second-set comeback, will now face either Federico Coria or Francisco Cerundolo in the next round.
In the other first-round ties, Yannick Hanfmann recorded a straight-sets win over Thiago Monteiro, while Elias Ymer, playing in his home country, beat Taro Daniel 6-2 6-7 (6-8) 6-4.