The horrific attack on Jesse Ryder has prompted a warning for people with a public profile to be on their guard.
The cricketer remains critical in Christchurch Hospital after a cowardly attack outside a bar in Christchurch.
Psychologist Sara Chatwin said sports stars and celebrities should realise they were always on show.
People needed to be wary when they put themselves in a situation where emotions could change, and peoples' switches could flick, she said.
Ms Chatwin said it was likely to be a tragic example of what could happen when alcohol or substances were thrown into the mix.