Goalkeepers are in a unique position. If they make a mistake, very often it ends with a goal being conceded. No other position has such responsibility. If a defender makes a mistake, then the keeper may be able to retrieve the situation. If a striker misses an opportunity he may well get the next one.
Bobby Gould threw a tantrum and dropped Randy Avramoivic after an error ( I think against Watford in the cup if I remember correctly but maybe wrong). He said publicly, that Avramovic would never play for CCFC again. He promoted a very young Perry Suckling and some say the pressure and constant playing of a young keeper ruined him. He went on to have a career in football but never made any team his own.
I guess the point I’m trying to make, is keepers more than any other position in my opinion need to be treated carefully, as once the confidence goes it can take a long time to get it back, if they ever do. Simon Moore, Mark Marosi being two I can think of but Simon apparently had personal problems which affected him. Mark had the horrendous injury. But the result was the same they both lost their confidence.