"When I got out of the court, when the doctors tested me, they said to me "Maybe it would be better for you to stop", the 33-year-old former world number five told reporters.
Cilic lived up to his status of team leader this weekend, winning his two matches without dropping a set.
The ITF said it expected the new format would help generate more money for tennis development around the world, but Mahut claimed tennis stakeholders should have come up with better solutions.
The hosts trailed 2-1 and needed to win both reverse singles on the final day to become the first team since 1939 to overturn a 2-0 deficit in a final, but their hopes of a comeback were soon dashed.
Croatia will enter the history books as victor of the last final played in the traditional format before the 118-year-old team competition gets a major revamp.
Indian island police struggle to get body of American
The group now fears that the survival of the tribe, which is believed to now consist of only 50 to 150 people, is under threat. His family wrote: "He was a beloved son, brother, uncle, and best friend to us".
He hung on grimly in the first set, saving a break point at 4-4 with a attractive dropshot. "There was a lot of pressure but I played a hell of a match today and deservedly won".
Cilic dictated matters in the tie-break at the end of a first set, in which Pouille twice held after saving break points, the 2014 US Open champion producing a fine off-balance backhand volley to forge ahead. Already secured their places in the final of the World group semi-finalists this season (Croatia, France, Spain, USA), and the remaining 12 will be determined by the results of the playoffs.
Pouille managed to save four set points in the eighth game with a series of fine serves before Cilic held his next service game to seal the set with a crosscourt forehand.
In the 11th game already Cilic had a great chance to break Tsonga made a unforced error and gave the opponent the second set. "I think they're handsome winners and they deserve it".
Chardy was outplayed by Borna Coric on Friday while Cilic beat Jo-Wilfried Tsonga who is a doubt for Sunday because of a muscle injury picked up in that straight-sets defeat.
Cilic is bidding for redemption this weekend after blowing a two-set lead against Juan Martin del Potro in the 2016 final when victory would have sealed Croatia the title, and their doubles pairing of Mate Pavic and Ivan Dodig could finish the job on Saturday. Playing two sets is not the Davis Cup.