A teenage midfielder who was heavily linked with a move to Manchester United prior to the January transfer window can certainly not be accused of lacking self-confidence. But there is a fine line between confidence and arrogance and, after eventually sealing a £22 million move to La Liga instead, the 19-year-old is not foolish enough to have been taken aback by his lack of first-team opportunities under Diego Simeone. “I knew that I would not play everything, and that I would have to adapt,” Arthur Vermeeren, as mature off the pitch as he is on it, tells DAZN, the former Royal Antwerp ace left…