Barcelona ended their LaLiga campaign with a 3-1 loss to Valencia but nevertheless won the title by eight points over rivals Real Madrid.
Los Blancos have experienced significant internal strife this season and Flick believes Barca will need to be even better than they were in 2025-26 if they want to defend their title.
While some players will have a well-deserved break, several of the players will also be heading off to represent their countries at the 2026 FIFA World Cup.
Flick wished his players well on their travels but made it very clear he would accept nothing short of 100% commitment when they returned.
"The World Cup is a big event and the players are focused, but next season will be tougher and I want everyone 100% focused," he said.
"Now we can go to the World Cup or go on vacation and rest, but what counts is Barça and when we return we will continue our journey and I want 100% commitment from everyone.
"I am prepared, I have that hunger, I want the players with that commitment, that everyone, players and staff, can give their best for this badge."
Marcus Rashford's future at Barcelona has received strong backing from teammate Frenkie de Jong, who believes the forward has done enough to remain at the club beyond this season.
Marc Cucurella has reportedly emerged as a major transfer target for both Barcelona and Atletico Madrid, with reports suggesting the Chelsea defender could be at the centre of a growing battle between Spain's top clubs.
Egypt have shocked many football fans after handing teenage Barcelona forward Hamza Abdelkarim a place in their squad for the 2026 FIFA World Cup.
Barcelona have confirmed that Fermin Lopez has undergone successful surgery after sustaining a fracture to the fifth metatarsal in his right foot.
