Qwiss iirc Havertz was always one of the most hard-working Chelsea players despite things not working out there, so his attitude was never in question.
Also, I'm not sure what about Arteta's managerial career so far has indicated that he's one to fix players' poor attitudes. His way of resolving that issue (which has worked out well) has been getting rid of said players the first moment he could, not 'fixing' them.
