Everton manager Roberto Martinez told his team they needed to develop a "nasty streak" to start turning performances into results.
The Spaniard saw his side held 1-1 by Norwich City on Saturday for what was their eighth draw in 16 Premier League games this season.
"You need to have that nasty streak in your own box when sometimes we are still thinking about trying to score the next goal and being creative on the ball," he said.
"That is what is going to make us a winning team, no two ways about it, but within a game there are certain moments when you need to be ruthless and have a nasty streak in order to keep a clean sheet.
"That is an area at the moment in which we are getting heavily punished."
Wes Hoolahan scrambled in Norwich's equaliser against Everton after a set-piece, with Martinez's men having conceded from a corner to draw with Crystal Palace less than a week prior.
"It is a problem at the moment," he said.
"You shouldn’t concede from corners at that ratio. A corner cost us two points on Monday, and we conceded a corner and it cost us two points [against Norwich]."
