It came as something of a shock after previously letting in just one in five league matches this season.
However, they have already experienced similar against AC Milan a fortnight ago when they let in two goals in three minutes just before the interval, resulting in a more difficult second half than they should have had before closing out a 3-2 victory.
“It’s not that much of a concern because I don’t think you should make these things bigger than they are – but we have to show a reaction, that’s for sure,” said Klopp before the squad flew out to Portugal.
“It’s really tricky to win a football game when you are not defending on your highest level and that’s what we didn’t do.
“The common opinion is it’s only about the last line but we had a problem in general with our defending. That’s why Brentford caused us problems and it wasn’t good.
“We have to improve in that department for sure but now is not the moment to be concerned.
“We spoke about it and we know we cannot do it like that. I think we have sorted it but we have to show it tomorrow.”
Liverpool’s last two meetings with Porto have seen them score 11 goals and concede just one and after both encounters Klopp’s side progressed to the final, winning one and losing one.
The Reds boss is not one for omens, however, and insists Tuesday’s match is a reset.
“It’s not an advantage at all that we won the last two games there, absolutely not. For them it is another reason to be motivated on the highest level,” he added.
“You only have to put yourself in the position of the opponent and the first thing you would want to do is make sure a similar thing doesn’t happen again.
“That doesn’t make our job easier for sure but it’s not about that. We don’t think about the last two games we played there. We think about this one.
“We didn’t think about the game before when we won 4-1 because it makes no sense.
“They qualify year in, year out for the Champions League and they are always first or second in the Portuguese League. That is a top team and that is what we are preparing for.
“I am still happy we won the games when we were there but we don’t think we have won this game already.”