I own one of Damien Hughes's books (the sports psychologist at Warrington). I bought it mainly through Red Issue Sanc to get an insight into what it is they do. The tactic in the book is to use the habits of successful people and extraordinary feats by those previously seen as unremarkable, such as
rlCliff Youngrl, and apply them to your life and the situations you're likely to be in. So the desired effect is for a player to think: ‘Well if those people can achieve what they did, surely I can too!’ Thus a psychological barrier is broken.
However, people who tend to big up sports psychologists are those who were excellent to start with; Raymond Van Barneveld’s ‘Zen master’ springs to mind. So I imagine a club would turn to a sports psychologist when as a solid unit, they are doing everything they can and everything right but still can't win honours. Especially with today's constraints i.e. the salary cap. I think we're some way from that position.