16U ASA rules. Team has 9 players in lineup plus 1 sub on the bench. Sub enters for a starter. Another girl on the field becomes injured and cannot play. Can the original starter go in for the injured girl, thus having the starter and her sub in the lineup at the same time, or is the team required to play with 8 fielders since they don't have any more subs?
Once a player has been put into the lineup, they cannot occupy another spot in the batting order, they are locked to that batting position. So no, a player and their sub can never be in the same batting order. The team would have to continue with only 8 players on the field and in the batting order if the injured player was unable to return. The vacant spot in batting order would also be an automatic out each time it came up.