How can you develop a proper training program without an analysis of what the athlete is capable of??? I think it is certainly worth your time to spend at least some time with an athlete before you give them a training program. The sooner imbalances are corrected the better and will hopefully lead to a better athlete who is more injury resililent.
It doesnt have to take a lot of time or resources. A quick video (using their mobile phone) of their squat technique and also their single leg squat control can sometimes tell you all you need to know about their lower body.
Looking at their posture will also let you know a lot about their upper body – is their thoracic spine kyphotic or are their scapula protracted???
I believe it is time well spent!