Getting out of a Slump
The first thing we need to take care of was his thought process. My recommendation to him was to learn and utilize the concept of imagery or visualization. I like to refer to these terms as your mental replay system in your mind. During the time when athletes experience below average confidence in their game, the replay system plays negative thoughts over and over in the athlete's head. These negative thoughts produce low confidence and can paralyze productivity. The trick then is to learn how to change the images in the brain to prevent focus on the negative and redirect to positive thoughts. This can be accomplished in a couple different scenarios and strategies.
The first strategy is before each game spend some time daydreaming or thinking about a previous performance that bring back some good memories. It really doesn't matter what the memory is as long as it is a positive experience in the particular area you are struggling with. Replay this scenario a good ten times or so. What you are doing here is essentially reprogramming your brain to release the negative frustrations associated with your failing at a certain task. Instead, your mind will begin to associate positive memories with specific movement with your body. Over time this will allow you to let poor performances go more easily
Secondly, use this skill during the game when you experience a failure. Maybe you walk a guy with the bases loaded, or pop out to the pitcher, or strikeout for the 3rd time in a game. Immediately following a negative experience, replay the above positive scenario in your mind. Instead of seeing youself walk that guy with the bases juiced, you will now begin to see yourself strike out the hitter. Enough of this type of mental practice and you will reduce the amount of slumps you'll slip into during the season. This takes some time and some concentration but the advantage is that once you can learn this skill, your mind will begin to do this automatically and therefore prevent itself from dwelling on the failures you experience each game.