The Spanish champions face United on Wednesday in the first leg of their Champions League quarter-final showdown, with the reverse fixture taking place six days later.
Coutinho, of course, knows the Red Devils well from his days at Liverpool and is fully aware of where the strengths in their side lie.
“It’s complicated to describe what you have to do to win against this team,” said the Brazilian, as per the Mirror.
“For a start, Manchester United have a great goalkeeper and huge players in attack.
"Pogba and Lukaku are capable of hurting any defence and Pogba, in particular, is a great player.
"We will have to be very careful to stop him because he can generate a lot of problems for us and I think the duel with [Gerard] Pique will be important in both matches.”
United head into the tie on the back of three losses in their last four, but Coutinho knows not to underestimate his old foes.
“United have had some inconsistent results recently, but it’s clear they have improved in every area under [Ole Gunnar] Solskjaer.
“For me, the key for both sides is going to be in attack. Whoever wins that battle will be in the semi-final – and I’m confident it will be Barca.
“If we play with our usual character and style, then we can win at Old Trafford,” he added.
The winner of the clash between United and Barca will take on the victors of Porto v Liverpool, which could potentially see Coutinho face his former side.
The 26-year-old joined the Catalan club from Liverpool in January 2018, for a fee of £138 million ($180m) and has admitted he would welcome a return to Anfield in the semi-finals.
“Let’s see, I hope it happens, but we have a big game first at Old Trafford,” he said.
“What I can say is that I’m glad that Liverpool are doing well this year and, if the draw had been different, I would have liked to play the Champions League final against them.
"Klopp is a great coach and it was only a matter of time before he got the team performing the way they are.
“They are having an incredible season, but so are we – and I am focused first on Barcelona.”