Harry Kane scored twice as Jurgen Klopp’s visitors suffered an afternoon to forget in defence, with Son Heung-Min and Dele Alli also on target amid further uncertainty at the back.
And a frustrated Coutinho, who saw home keeper Hugo Lloris produce a spectacular stop to deny him a consolation strike, said: “The goals were goals that could have been prevented.
“It started out wide and we end up conceding one of those goals the manager speaks about.
“He speaks a lot about this — we’ve conceded a lot of goals like this. And obviously in attack we were unable to score the goals necessary to draw or turn around the game.
“We were in the game during the first-half then the goal we conceded made everything worse.”
Liverpool have conceded 15 goals away from home, the most in the Premier League this season and three more than bottom club Crystal Palace.
But Coutinho said he believed the problem was “not just down to the defence, it’s the whole group.”
He added: “The first goal started in a wide position where everyone is involved in defending, not just the players right at the back.
“We have to improve this as quickly as possible in order to win games and fight more. With difficult games like this one, we know it’s these things that decide them.
“So we need to concentrate more to deal with balls like this.
“The first goal was scored after four minutes and the second one after 12 or 13. It’s difficult to play away from home against a strong team when you start like that.
“We have to work hard. Those passages of play, those set pieces from wide positions. We have to concentrate more to deal with them.”