Young players will always copy their heroes on the pitch but sometimes they copy the bad things as well as the good MORE
How can I give a confidence boost to a leaky defence?
The trick is to take the pressure off those players specifically, and place it onto the shoulders of the rest of the team. So instead of defending as a three or four, now defend with all 11 players.
Thus, pressing is the name of the game, with strikers tracking back, midfielders squeezing space in the middle and wingers coming back to help in deep defensive flank positions.
Maybe, for a game or two, suspend some of your usual attacking ploys and concentrate purely on the whole team defending deep.
I guarantee doing this will see an improvement in defensive performances. players are pressing high up the pitch and tracking back to help team-mates.