CARLTON defender Michael Jamison says the Blues' mental approach cost them a possible top-four spot after suffering an upset 29-point loss to North Melbourne at Etihad Stadium.

After recording wins against 2009 finalists Geelong and St Kilda early in the season, the Blues have stumbled against both Hawthorn and North Melbourne in the past four weeks, putting their chances of a top-four finish in serious jeopardy.

The 24-year-old was frustrated with the Blues' inability to beat sides below them on the ladder and believes the club has plenty of work to do before they consider themselves genuine contenders come September.

“I think it is how we come prepared and approach the game,” Jamison said on Friday night.

“I don’t think we take teams lightly if they are below us but it’s something we will have to address pretty quickly because you don’t go too deep in the finals not winning many games in the row.”

“I think it is trying to maintain the same approach and intensity throughout the whole game.”

The Blues have yet to win three consecutive games this season and the defender was at a loss to explain the mental lapses that continue to cost the team.

“I wish I knew,” Jamison said.

“It keeps happening. If we did know, it wouldn’t happen any more. It’s not because we are a young side - it’s something we have to address quickly and we will look at during the week.”

Despite reducing North's lead from 38 points to just eight late in the third quarter, Carlton could not convert its chances in the final term, kicking just four behinds when the game was in the balance.

“We got back into the game - there were a few stages throughout the game where we were only a couple of goals behind,” Jamison said.

“Our midfielders seemed to work hard enough to get the ball in there but we were just kicking it to the wrong option most of the time.”

“I think it was more what we did wrong rather than what they did right.”