Yamal picked up the groin injury earlier this month, but still joined up with the Spanish national team. The youngster then aggravated that problem while playing for his country, prompting Barca boss Flick to accuse La Roja of not taking care of their young players.
He said earlier this month: "Lamine goes to the national team with pain, didn't train, had painkillers to play, they were three goals ahead in every match, and he played 79 and 73 minutes. Between the matches, he didn't train. This is not taking care of players. Spain have the best team in the world, in every position they are unbelievably good. I am really sad about this [situation]."
The former Bayern Munich manager also admitted the communication he has with Spain boss Luis de la Fuente could be better.
"I never really spoke with [De la Fuente]," he added. "Maybe my Spanish is not good, his English is not good, so this is a problem. Normally, the communication, because we have more players there than just Lamine, could be better. I was also on this side as a national team coach, so I know how hard this job sometimes is, but the communication with the clubs was always good."