Through my years coaching I have seen (mostly parents and almost always fathers) that try to be both swing coach and caddy. It is the very rare case where this works out for the player. This is because coaching and caddying are two completely different jobs. So let's compare and contrast.
Coaches have to be both supportive and encouraging, but they must also be critical. They must be firm and honest with a player when they are not swinging correctly, practicing well, etc. A caddy on the other hand must be a cheerleader (100% of the time) and sometimes psychologist/psychiatrist. unlike a coach, the caddy must never be critical. So by definition these two positions conflict.
Yet I have seen where a parent has raised a champion level golfer being both coach and caddy. But in 10 years of coaching I have only seen two successful examples.
In both cases the parent understood the difference between coach and caddy and therefore never coached while caddying. They both allowed their player to make mistakes during the round and would only be critical after the tournament or round was over. But in 99.9% of the cases the urge to coach while caddying is just too great and the parent will start telling the player that they are gripping the club wrong, their swing is too long, they should have hit a fade over the water instead of a draw.
Most parents have a strong instinct to help and protect their kids. Standing by and watching them take their lumps while playing is just unbearable for those that think a few words will fix what is going wrong at the time. But coaching during a round of golf is annoying and confusing to the player. Coaching during a round is like helping a kid while they are taking a math test. Like an academic test, a round of golf is an evaluation of the players efforts to date. Any coaching during a golf test only skews the results.
But there is always an exception to every rule. In this case one must play the role of coach during a playing lesson. But playing lessons should be designated as such before stepping on to the first tee. And it should be clear to the player that they are getting a playing lesson and score is of zero consequence.
Understanding the difference between caddies and coaches will accelerate the learning process and increase the trust between the player and his support team.
If anyone has opinions or experiences they can share on this topic, please leave a comment.