While Mohamed Salah, Sadio Mane and Roberto Firmino will be a primary focus for Barca in the Champions League semi-final first leg on Wednesday, Coutinho praised Jurgen Klopp's midfield and defence as he looked forward to lining up against the Reds.
The Brazil international spent five years at Anfield, during which Liverpool finished second in the Premier League and were runners-up in the Carabao Cup and Europa League, but they have since emerged as one of Europe's strongest sides under Klopp's guidance.
Coutinho told Barcelona's official website: "They are a great team. They are very strong mentally.
"I have been watching them all season and they are excellent going forward and in defence, so we will have to be very alert.
"There are important players for them but it's not just those three [Mane, Firmino, Salah]. There are the defenders, the midfielders who are all quality players and work hard to create goals for the team.
"We will have to be aware of the whole team and do our jobs as we have recently."
Barca team-mate and fellow former Liverpool star Luis Suarez echoed Coutinho's comments and highlighted similarities in how the two teams play.
"Liverpool have a way of playing that might surprise people, but they can play out from the back and have excellent players in midfield who can get the ball to their strikers," said Suarez.
"They can play in a way that is similar to our way of playing. I don't think there is that much difference. What is true is that both teams are very strong and the other one will have to look out.
"Obviously it's exciting to be going back to play at a ground like Anfield where the fans looked after me. I talk to [Jordan] Henderson a lot and he's obviously looking forward to playing against Philippe and myself and that will be special but now each one is playing for their team and doing their best.
"I remember the people there with a lot of affection. I speak to people who are still there and they miss those moments that we had together."