I recruited a guy that I played softball with several years ago to play on our team this year. He has been suffering with dementia for several years and this will be his last year of playing. He has very good physical abilities, but has problems finding his bat and glove, does not know what to do with the the ball if it comes to him, and can only run to first base as beyond that he doesn't know when to stop. His wife told me how much he is enjoying playing and I am glad we were able to provide some happiness for him. It is quite sad to see how this formerly great player has declined, and it's even noticeable as this season has progressed.
So bend the rules a little for him. Have him wear ear buds so someone can tell him what to do via cell phone - stop at first, go on to 2nd. Throw it to the shortstop. It may be the decision process that's deficient - but he could orient towards the lifelong known landmarks of a baseball diamond.