Luis Enrique first contact with players came less than two weeks ago in training camp. He immediately imposed his energetic style in the practice sessions, and it translated onto the field in the first two matches.
It was the biggest defeat ever for Croatia, who were playing their first competitive game since reaching the World Cup final in Russia.
Portugal did not need Ronaldo - who skipped international duty to recharge after a busy summer - to beat Italy 1-0 in Europe's newest soccer competition.
Mbappe, who was the first teenager to score in a World Cup final since Pele in 1958, netted his ninth goal for France.
The football fervor that swept through England during June and July was punctured by a 2-1 loss to Spain.
Brazilian-born midfielder Jorginho converted the spot-kick after substitute Federico Chiesa earned the late penalty for Italy.
Chiellini was one of a number of players who announced they were quitting the national team after November's playoff loss to Sweden saw Italy fail to qualify for the World Cup.
Germany and France headlined the opening night of the UEFA Nations League, it was the 2014 world champion against this year's winner but the upshot was a 0-0 draw.
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