Sunderland head coach Dick Advocaat admitted to feeling a degree of fear at his side's showing in Saturday's 4-2 defeat at Leicester City.
Adovcaat masterminded Sunderland's Premier League survival last term but, having been persuaded to stay on at the Stadium of Light, endured a miserable first game of 2015-16.
Jamie Vardy and Riyad Mahrez's brace ensured a dominant half-time lead for Leicester, before Jermain Defoe threatened a comeback.
The impressive Marc Albrighton restored the hosts' three-goal lead and, while Steven Fletcher had the final say at the King Power Stadium, Advocaat was given plenty of food for thought.
"Not only the result scares me a little bit, but also the way we played," explained the Dutchman.
"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."
Lee Cattermole gave away a penalty when he was bamboozled by Mahrez inside the area before the skipper was hauled off on the half-hour mark as Advocaat switched to a 4-4-2 formation.
The Sunderland boss highlighted Cattermole being on a caution as a reason behind his decision - despite the midfielder not entering the referee's book.
"Lee Cattermole, like others, was not in the game plus the fact he had a yellow card," Advocaat added.
"Hopefully we will learn from this and next week we can do better than we did today."
