Fall baseball is important prep for the season. There are a few guys who get an opportunity to work their way on to the spring roster, but the focus is on building the lineup that will take the field against Duke.
Some veterans are pretty secure and use the fall to develop their skills, but I doubt that a single position was set coming into the fall. That is true to a much greater degree than the fall practice in 2010 and 2011. Thompson, Turgeon, Tobias, Ramjit and a few others know they will play most of the available innings, but there's a chance they'll play in different positions in 2013. For example, Ramjit has been working in RF this fall. Other experienced players, including Powers, Dent, Shafer and Gushue are battling for starting jobs and certainly for innings on the field.
Richie Martin may win the SS job, but other frosh want playing time, too, including pitchers. Certainly, preseason practice in January and February is when the opening lineup is decided and offseason workouts matter, too, but fall practice is much more than a tryout period for walkons.