The Black Cats fell to a disappointing 2-1 defeat at Birmingham this weekend.
“It is very disappointing for us, but it’s not the first time this season after some good results,” he said.
“Especially when we have won at home sometimes, we can’t keep our level of play – and we must turn that around in future games.
“Everybody knows the potential and quality of our team. But it’s a hard league, and you have to be 100 per cent concentrated all the time and start well in games.
“We must learn from that and change our mentality to keep our level over two or three games.
“We have a lot of work to do.”
