Just a matter of confidence that I can relate to from my junior tennis years. People speaking "ah he's shite, Morata is better, he is just a speed merchant" they know jack shite of what goes through anyone's head when they hit a rough patch.
Back in my junior days I beat two guys that are CURRENTLY in top 30 ATP rankings and I beat them twice in the span of two months, four matches against them I did not lose a set, then I had some personal issues, my confidence got shot, I lost some matches I was not supposed to, I was on a losing streak and half an year later I played against these two guys again and they beat the shit out of me this time (60 61 both matches iirc) and they even asked me what the hell it happening to me.
Six months earlier I'd have beaten them any hour of the day and the night, six months later I could not even win two points in a row to save my life - confidence plays a big part in any sport and mine was shot at that moment.
I think Werner is in a similar spot now, English media is all over him, he does not have the same input as he used to and lately that Bild article and the fact that Low does not trust him anymore might have shot his confidence even harder.