Dick Advocaat has admitted that he "can't understand" why Sunderland's defence has performed so poorly at the start of the Premier League season.

The Black Cats have conceded more goals than any other side in the top flight so far, letting in seven goals in just two fixtures to leave them at the bottom of the table.

"I didn't want to change the back-line already after one game. But at the moment, there are players playing who I can't understand why they are playing that way," the Sunderland Echo quotes the manager as saying.

"I cannot understand it, honestly. But there must be a reason and I hope that they can tell me. I spoke to the players and told them that we like full-backs, who if the possibility comes, they go forward. But I've changed that. I've now set up a different way.

"The first way for the back four is now defence. And then the opponent cannot get the kind of space they got at Leicester. Take care of your man, and beside that, if you can do a little bit more, then go forwards, otherwise not. We have to change the basic facts."

Sunderland host Swansea City in the league on Saturday.