Arsenal captain Cesc Fabregas believes key errors are to blame for the Gunners' disappointing recent form.
The Spain international, who continues to be linked with a return to Barcelona, was unhappy with the two goals Arsenal conceded in Wednesday's Champions League last-16 first-leg defeat at FC Porto.
Goalkeeper Lukasz Fabianski and veteran defender Sol Campbell were both at fault for making vital errors at key times as Arsene Wenger's side lost 2-1 in Portugal to leave the second leg at the Emirates Stadium on March 9 on a knife-edge.
Fabregas criticised the team's 'schoolboy defending' after the game and has since added: "The other top teams don't make these mistakes as often as we do. Sometimes we make mistakes that at the top level you pay for and this is one of those nights.
"It happened against Chelsea and Man United and now again so I think we have to try to find the solution to these problems because it is costing us many, many things."