Zlatan, no comment needed.
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Lol. He is the king of the cockiness.
But on more serious note, it s not that simple. Cockiness can easily point to the oposite. Cowards are often the loudest in the group. They just compensate their fear with cockiness.
Also, people are not mental static point in time. Specialy if you look at the (young)player in a small time frame. It s hard to judge other peoples mentality, since usually we are not even aware of our own.
It s best to make conclusions based on their actions. So...let s wait a full (healthy) season, before deciding "he is not gona make it".
If Dembele had this look in his eyes, I would put my money right away on him that he will be the next Ronaldinho and an ultimate leader, key player, decisive in tough moments etc:
That look was an admiration, not determination