| Not really an opinion, more a set of observations:
If we don't know how long the sportsman has been with the 'new' coach, it's not possible to even guess the extent of their influence.
If you've been with someone for a long time, you may develop habitual responses to their coaching efforts. Now a top coach may be able to shake you out of a rut, but sometimes just going to someone new gives a slightly different angle on things (not necessarily different, but explained in a new way, or from a direction that makes it new).
Sometimes someone new telling you something you already know gives it fresh impact.
Without knowing the individuals involved, it's really impossible to comment more specifically (and maybe not even then). |