For some teams that have a few weak links on the field, or hae some bowlers, or batsmen, very tired, they could probably use a substitute fielder every once in a while, as it happens in one-dayers. Do you think they should keep the substitutes on the field a little longer by periodically replacing a different player each time? Could the same be used in Tests? You could pick a few players (at least 1) just as substitute fielder so that you could bring him on to field when needed. In some long tours, someone might always end up a journeyman and not a player. In his place, we can have such players, picked for fielding. Your opinion?