Manager David Moyes accepted that his side's defending had not been good enough in their 2-2 draw away to Premier League newcomers Hull City.
The Toffees had to fight back from two goals down to secure a pint at the KC Stadium, with both Tim Cahill and Leon Osman netting in the final 20 minutes.
Afterwards, Moyes admitted: "It was two set-pieces, the first one we got out-jumped on, the second was just poor communication and bad defending.
"It's not the way we want it. I think a lot of it has been down to communication and understanding.
"Normally we are very good at it, but at this moment in time we are not, so we are going to work even harder to get back to the standards we set last year.
"These things can be corrected, but we've been making a few individual mistakes as well and if people keep making mistakes, they have to be accountable.
"We can't continue conceding goals the way we're doing just now.
"The players worked really hard, but we know that is how they are, but I'm disappointed we didn't win the game."