Dick Advocaat has admitted that he is fearful of what is to come after watching his Sunderland side lose 4-2 to Leicester City on the opening day of the new season.

Leicester raced into a 3-0 lead at the break before the Black Cats hit back through Jermain Defoe, but Marc Albrighton added a fourth to the hosts to ensure that Steven Fletcher's goal was only a consolation for the visitors at the King Power Stadium.

After narrowly avoiding relegation last season, Advocaat concedes that there is clear room for improvement following a disappointing start to the new campaign.

"Not only the result scares me a little bit but also the way we played," the Sunderland boss told reporters.

"Especially in the first half, we know what we have to do and we have to change some things. The first cross is a goal, the second cross is 2-0 and, by the third, the left full-back is sleeping.

"They were sharper and they were better. We gave so much space away and we know that they will come. They had space up front."

Sunderland host Norwich City at the Stadium of Light next Saturday.