"It told everyone which direction this club wants to go," he told the Sunday Express.
"There was a lot of pressure on Mesut when he joined us, but he has dealt with it fantastically well and now we know we can play against any team.
"It gives you great confidence when top players come in. Psychologically, it is very different to when you see your best players leaving.
"We have more confidence. We are winning games that last season we were drawing. We have been able to handle it when we have tough moments. We are able to get the points at the end."
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