Croatia moved one rubber away from winning their second Davis Cup title after taking command against reigning champions France in Lille on Friday.
Borna Coric got Croatia off to the best possible start with a straight-sets thrashing of France’s Jeremy Chardy in the opening singles.
The world No 12 galloped through the opening set as Chardy’s service temporarily collapsed and went on to win the match 6-2 7-5 6-4 in two hours 19 minutes.
Then former US Open champion Marin Cilic saw off Jo-Wilfried Tsonga 6-3 7-5 6-4 to give them a handsome lead after the opening day.
Croatia, who were the first unseeded nation to win the title against Slovakia in 2005, will now hope their doubles partnership of Mate Pavic and Ivan Dodig can complete the job when they face home pair Nicolas Mahut and Pierre-Hugues Herbert on Saturday.
France are looking to win back-to-back titles for the first time since the early 1930s but now must come out on top in the remaining three matches over the next two days.
Sunday’s reverse singles would see Tsonga face Coric and Chardy take on Cilic although the captains are allowed to change their teams.
Tsonga is doubtful for the remainder of the final, after injuring his groin during his loss to Cilic.
The Frenchman was hurt in the third set of his defeat and said he will undergo exams on Saturday morning that will determine whether he is capable of playing on Sunday, if France extends the tie to the reverse singles.
Tsonga said he was advised by team doctors to consider retiring against Cilic, after taking a break in the third set to receive medical treatment.
The final, being played on clay inside the 28,000 Stade Pierre Mauroy, is the last one before the century-old competition is revamped next year.
The 2019 competition will do away with the home and away format after an opening qualification round and will culminate in an 18-nation finals week in Madrid in November.