If you (and the opposing coach) are convinced that the team really only has four valid jerseys (maybe they started out with only five and one got torn so badly that it is unusable) then I'd make an exception, depending on the level of play (and from what I understand of the Texas levels, this game sounds like it would qualify, playoff or not). If they have only five, I would allow for some extra time every now and then for them to be able to substitute linemen during long offensive drives, if needed.