France's hopes of retaining the Davis Cup suffered a major blow as Croatia opened up a 2-0 lead on day one of the final in Lille.
Borna Coric and Marin Cilic each triumphed in straight sets for Croatia against Jeremy Chardy, who was somewhat surprisingly selected ahead of Lucas Pouille, and Jo-Wilfried Tsonga respectively.
As a result, France must win Saturday's doubles, which will see Pierre Hugues-Herbert and Nicolas Mahut take on Ivan Dodig and Mate Pavic, to have any chance of repeating their victory in 2017.
The hosts were enthusiastically backed by the majority of a crowd numbering close to 20,000 at Stade Pierre Mauroy, but Coric, who has risen to 12th in the world rankings, looked composed as he beat Chardy 6-2 7-5 6-4 in the opening singles rubber.
The 22-year-old did call for a medical timeout late in the contest, due to an apparent groin strain, but insisted it was only precautionary.
"I'm okay," Coric was quoted as saying by the Davis Cup's official website. "I had this problem since basically Shanghai. I started to feel it a little bit towards the end of the match but it was just fatigue."
"I feel like I can play for five hours, there's just a little bit of pain so I thought it was better to get it treated then instead of later in the match."
Tsonga, down at 259th in the rankings after prolonged injury troubles, also appeared to be hampered by a groin problem in the third set of his 6-3 7-5 6-4 loss to world number seven Cilic.
An emotional Tsonga cut a forlorn figure after the match and received sympathy from his opponent, who said: "It was bad luck for Jo. The first two sets were a high level, I played great tennis."