"It's always good when a player smiles, but not every day is the same. I don't smile every day either," Flick said ahead of Barcelona's match against Rayo Vallecano.
"Everyone is worried about him, but he played a World Cup after an injury. He had three weeks of holiday. He's played two matches - the first maybe wasn't his best, but I'm happy because he gives us more, he creates chances. Against Athletic he played the full 90 minutes, and I saw him at a top level.
"Today he was excellent. He's on a very good path. We have to support him, and I'm going to do that."
Flick was equally content with the broader state of his squad heading into the closing days of the transfer window, even as he left the door open to late additions.
"I'm happy with the team I have. Deco is working to see if we can strengthen it further. But we're under no pressure. He's done a fantastic job so far. For me, everything is fine. I see quality in training, and we're in a good place. We're on the right track," he said, adding that in an ideal world business would be wrapped up before the season starts, "but there are things I can't change."
On individual situations, Flick confirmed Joan Garcia remains first-choice goalkeeper ahead of new signing Dominik Livaković, "a signing for the future" the club is pleased with, while defender Álvaro Cortés is expected to leave on loan, with Flick noting "it's good for him to play in Belgium" given his lack of first-team minutes in Catalonia.
Frenkie de Jong, meanwhile, "has improved" and remains central to Flick's plans despite a heavy World Cup workload requiring careful management: "The team is the priority, not me, not a player. It's the club."
Asked to weigh in on the Ballon d'Or, Flick declined the invitation.
"Deciding who will win the Ballon d'Or? That's not my job. Mine is already difficult enough without tracking that too. I have a lot of good players in my team. I'm not a fan of these things. I care about the team - if it succeeds, there are more chances of winning individual titles. There are world-class players and it's not easy to choose just one."