Liverpool boss Jurgen Klopp says their defensive display against Brentford is "not a concern" going into the Champions League group game with Porto.
The Reds' 3-3 draw on Saturday was the first time they conceded three in a match since the European defeat by Real Madrid in April.
"We didn't defend at our highest level so we have to improve," said Klopp.
"We don't make these things bigger than they are but you have to show a reaction."
Liverpool came from behind to secure a 3-2 victory in their Group B opener against AC Milan after going 2-1 down before Mohamed Salah's equaliser and Jordan Henderson's 69th-minute winner.
Before the Brentford draw Klopp's side had let in just one goal in five Premier League matches - against Chelsea - after an impressive start to the season which sees them top by one point.
"It's not a moment to be concerned but we have spoken about it and we know that we can't do things like that. We have sorted that and we have to show that tomorrow," added Klopp.
"This is a tough group and we should not waste time."
Thiago Alcantara and Harvey Elliott are sidelined by long-term injuries, but Klopp reported no new injury concerns and said he will be taking a full squad to Porto.
Liverpool thumped the Portuguese side 6-1 on aggregate in the 2018-19 quarter-finals, but Klopp said that record "is not an advantage at all".
Porto, who drew 0-0 against Atletico Madrid in their first Champions League group game, reached the quarter-finals last season where they were knocked out by eventual winners Chelsea.