Unai Emery blamed himself for Aston Villa's defeat at Monaco but reserved his harshest criticism for some of his players.
The Villa boss accused his side of lacking ruthlessness in front of goal and suggested not all his team had the mental strength required for elite football.
'We are being very demanding with the players and some of them are not following the plan,' said Emery, who admitted the decision to pair Jhon Duran with Ollie Watkins after 55 minutes had backfired.
'This is my objective now, to build the team to be as strong as possible with a mentality we are building progressively.