The Reds are still recovering from Tuesday night's collapse in Sevilla, where they blew a 3-0 lead to draw 3-3 in their Champions League tie.
“We were really ruthless in the first half and if you are 3-0 ahead against Sevilla away you have to play smarter," the Dutch international told LFC TV.
“I don't think it is a bad result to get a draw in Seville but the way we gave it up I don't think is a good sign.
“It is painful when you look back at the game but we have to go again Saturday.
“We have to speak with each other, lift each other up, put this behind us and concentrate on Chelsea."