IT was like watching a car crash: Katerina Johnson-Thomson's catastrophic Olympic javelin performance in Rio, where she slipped from third before the penultimate event and out of medal contention. Watching the anguished, anxious exchanges between the World indoor champion and coach Mike Holmes felt like an intrusion on private grief. Her spear was more paper dart than javelin and she finished 28th of 30 competitors, and a traumatised sixth overall.

Holmes has coached her since she was 15. Though one of UK Athletics' most experienced coaches (32 years on their staff) and a former throws champion, there have been hints that UKA would like KJT to switch coach – despite Holmes having enlisted both Mick Hill and Goldie Sayers (respectively World and Olympic javelin bronze medallists) as specialist advisers.

Johnson-Thomson once paid tribute to Holmes on her website for her portfolio of titles and medals: "Couldn’t have done it without you!" Yet she may now have to, following reports yesterday that she and Holmes are parting company.

Johnson-Thomson is reportedly not keen to leave her native Liverpool, so finding a new mentor may be problematic, although Tony Minichiello, coach of former Olympic and World champion Jessica Ennis-Hill, is waiting for his protege to decide whether her career is over.

Coach/athlete relationships are delicate, frequently fraught, and often defy logic. Youngsters, often not even out of primary school, go along to the local athletic club and are taken under the wing of a club coach. A decade on, if that kid is very talented and very lucky, they may progress to international level, and even Olympic representation. And their athletics career is often still in the hands of the coach who picked them up by chance on that first night down at the club. A classic example is Jimmy Hedley, the Geordie who steered Steve Cram from schoolboy athlete to World champion.

Educators, primary and secondary teachers, college lecturers, tutors and professors, all have distinct skill sets, yet athletics often works in defiance of educational principle. One akin to the primary teacher remaining the guiding educational force through secondary, university, to post-graduate doctorate mentor.

If one set out to design a coaching model, this athletics template would be rejected. One would surely go for a structured, progressive pathway. Yet this perverse system often works, and the sport should be grateful, for it's the main entry route for coaches – parents take their kids to clubs, then stay to help long after their children have left.

However, the ability of coaches to recognise that their athlete has travelled further and faster than they themselves have (very often while learning their trade "on the job") is beyond many coaches. It's a seductive thought that your athlete may make it to top level, and understandable that the coach might want to go all the way with them.

It's rather like being a parent: giving your children roots to grow and wings to fly. Knowing when to let go is the hardest trick, both for parents and coaches.

Parents make the best – and worst – coaches. Consider the abusive relationship between Damir Dokic and his tennis prodigy daughter, Jelena. Yet it can also work well, notably in athletics between Seb Coe and his father, Peter, while topically we have Robert Hawkins who delivers a workshop today at Glasgow's Emirates, venue for the scottishathletcs coaching conference. He has steered his sons, Callum and Robert, from Kilbarchan club level to the Olympic marathon. And tomorrow Trevor Painter presents a workshop on coaching his world 800m medallist wife, Jenny Meadows.

In tennis, the relationship between Judy Murray and her two sons has delivered glittering success. Initially Jamie and Andy's coach, she has developed more as performance manager, and remarked on one of Andy's early changes of coach that part of her skill was to recognise when a coach-player relationship had served its purpose.

Yet I know of coaches who have had to confront parents who think they know better.

In team sports, especially where significant money is involved, the dynamic is different. Players (left off the team) are often at odds with the coach (or manager). And this has now spilled into sports where significant Lottery funding is at stake, notably Jessica Varnish whose complaints against cycling coach Shane Sutton led to his resignation. Yet the Aussie appears to have more supporters in the GB team than detractors.

In rugby, we have another dimension, exemplified by a pending legal action between former Sale Sharks scrum-half Cillian Willis over allegations that the club was clinically negligent over a concussion injury. The formal duty of care is a dimension of sport alien to my generation, but rifts between coach and athlete are not.

When Allan Wells parted company with Charlie Affleck, to be coached by his wife, relations were less than cordial. Liz McColgan split acrimoniously with John Anderson and was coached by husband Peter; and Yvonne Murray parted from Bill Gentleman, her former school teacher, and switched to Tommy Boyle – also a discordant parting of the ways. All had been successful partnerships. And so were the new ones – with global medals which placed them among the most successful athletes in Scotland's history.

There is an old coaching maxim: every athlete is an experiment of one. Methodology and philosophy of coaching is broadly acknowledged, but the application to each athlete is unique. The art behind the science.

Scottishathletics is basking in the glow of having had a record 15 athletes in the Rio Olympic team. Rodger Harkins, who will introduce today's Emirates conference (9.30am), is perhaps best known as mentor of Lee McConnell, but his role as the governing body's director of coaching may prove his greatest career marker.