[Yoda]

What is the single most important attribute that a caddie must possess in order to be successful on tour?

First and foremost, the caddy must be trustworthy. This includes the ability to act independently as necessary to fulfill that trust.

Trust is the all-encompassing attribute. A player has many concerns, and his caddy serves to minimize or eliminate many of them. He should never add to them.

For example, the caddy must be trusted to show up -- on time -- at each event and on each day of the event (and, most certainly, for tee times). When entrusted with the player's clubs, they must be there, too (but no more than 14 before each round!). He must be trusted to perform, with a minimum of oversight, all his assigned duties (and some unassigned). Most of all, he must be trusted to 'handle with care' (and confidentiality) his player's innermost thoughts and emotions -- both on the course and off -- as revealed under competitive and personal stresses. We all have vulnerablilites, and the professional golfer is no exception.

In short, the player-caddy relationship is like any other. For there to be any chance of long-term success, there must be trust (both ways).

There is no substitute.