The problem with team defending one goal lead is always knowing
when to do it and which team are you playing against.
Some years back, teams defending small leads against ManU always
end up losing because ManU of the past has this drive to put things
right...that is, they are not here to lose.
If you score a goal in the first half or early second half, to
defend this lead immediately afterwards with tons of defenders and
1 striker is stupid. Eventually the attacking team will wear you
out.
If you defend a lead into the later stages of the second half, then
you can frustrate the attacking team because they don't have time
on their side. They may panic and attack without a cohesive
plan.
This is very obvious in the Everton v Chelsea game. They allowed
Chelsea too much time to attack and too much time on the
ball.
When Chelsea equalised, it was too late for Everton to come up with
anything.