I’ll add a little to Tom and Kat’s terrific responses. How old is your player? Have you asked the player how he’s feeling? What he’s feeling? And what you can do to help him? Listening to understand the players developmental needs and goals will not only help establish a solid coach-player relationship, it will enable you to have a far better knowledge of what the player likes, dislikes, needs, and how you can deliver it for him. Too often when we coach, we project onto our players what we would like to see, but without checking for understanding we’ll never know if our message is being delivered which means it’s less likely to be applied on game day.
Confidence is influenced by past performances, and training is part of that. Can you provide him with successful experiences in training? It’s also worth noting that confidence is influenced by social comparison, so if he is measuring himself against a teammate, an opponent, or the expectations of others, it’s important that he comes up with action steps to address his own realistic personal expectations that you can help him with. Understanding what sources of information work for your player(s) to enhance confidence will help greatly.
You mentioned that he missed big chances and the team ended up losing. How has that message been delivered to him and the team? Does he feel the team lost because of his missed chances? Does the team feel it’s his fault? Being able to attribute success and failure in appropriate ways where no single players feels they are to blame for a loss is critical. Identifying effort, performance, and attitude as productive actions will likely see the players confidence increase.