Its strange/interesting how keepers have bad patches and go from good to bad - bad to good...
Outfield players falling off makes more sense, they have more decisions to make, passing, shooting, dribbling also loss of pace and fitness, putting on weight etc all contribute to poor form, which again does not really effect a keeper...
With keepers. alot of it is down confidence which I think has a cognitive effect on decision making which leads to silly mistakes, like balls slipping through their hands (pause) and dwelling on split a second decision, which when confident is second nature...
The main thing when you ARE a proven world class keeper, like DDG, is having confidence and backing yourself... Once that is back and you instinct is on 100 your normally back on form...