One of his weaknesses sometimes turns into a strength....
He is very hard on himself and sees every fielding error or strike-out at the plate as a personal fault/failure to be eradicated.
What makes it a strength is a driving need to work on the problem over and over.
In some ways, it is self-defeating because, of course, he will make another error and he will strike-out again but in other ways it improves his game due to the amount of time and effort he puts in off the field.