Timing, pal. Timing. Also, the kind of manager that doesn't let his people talk back is a shitty manager anyway. I'm in a very open dialogue with my personel. Mistakes happen, deal with it... at the right time. Not right after the freaking mistake when he's loaded with adrenaline and frustration. The sub speaks for itself and is the strongest signal.
PS: I actually studied sports management before physiotherapy if you want to know.
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It's useless and it's proven by the actual reaction. Call him out the next day and it'll stick much longer. Now it only adds to the frustration for a player we need... Unless you're counting on Kean as a starter all of sudden.