If I were 3-1 up I would play my B team and simply keep 3 key players on the bench just in case. Depending how many points clear at the top of the league you are mind.
that`s what i`m doing playing the 3 in the league but leaving out of cup as i should go through with reserve strong enough for cup and i`m 9pts clear in 1st but i`m playing 1 of 5 Thai teams in my league and don`t want won`t lose as i`m 6-0 up with wins against them