Walk-ons honestly won't see much much time unless they really show something to the coaches (my playing time was very limited...alot of splinters were collected and heard some great jokes; I was not a stud by any stretch of the imagination).
Pitchers have the best shot. Position players may get in during blowouts or pinch hitting but realistically are going to ride the bench during most games. Best shot most walk-ons have will be an injury situation to a starter. My career (??) was cut short due to a severe ankle injury that didn't heal well...I don't think some of the coaches even knew I was gone.