Henry says Flick's "rigid" tactics were to be blame for their Champions League defeat to PSG at the Montjuic stadium.
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He told CBS Sports: "You can't play in the Champions League with that high line, I'm sorry.
"Against the big teams, you're inevitably exposed. Every move can turn into a goal, and that's exactly what happened against PSG. We've been saying it for a long time, but they didn't want to change."
The World Cup winner added: "Coaches can be stubborn with their strategies, but in crucial matches, this can be costly. Barcelona must learn to be more cautious if they want to return to being a leading player in Europe."