"I think I'm never going to get over it," Mbappe said, speaking 10 days after he scored a hat-trick in the final against Argentina which the South Americans won in a penalty shootout.
Mbappe said he had been through some "difficult times" since the defeat but he showed few signs of the setback in Qatar as he won and converted a 96th minute penalty to give PSG a last-gasp 2-1 win against Strasbourg on Ligue 1's resumption following the World Cup break.
"As I said to my teammates, there is no reason why the club should pay the price for the failure of the national team, they are two very different situations," 24-year-old Mbappe said.
"It does me good to come back with a win and to have a link with the club, the supporters and my teammates."
Sports website Marca.com quoted Mbappe as saying ""I spoke to [Argentine Captain Lionel] Messi after the match, I congratulated him. It was important for him, for me too, but I lost and you have to show maturity to congratulate the opponent."
