Gunner passes on some advice to the Premier League winners concerning how they can keep the Catalan club at bay, and believes they have a better chance than Arsenal did
The Red Devils will lock horns with Pep Guardiola's men at Wembley, having lost the same fixture in Rome two years earlier.
For his part, Wilshere saw his own side bowing out of the last 16 in the tournament at the hands of Barca, but received high praise for his performances against the Catalan club.
"The thing with Barca is three passes - bang, bang, bang - and they're through. So you have to get in their faces," he said, according to the Daily Telegraph.
"You have to stop the players like Xavi, Lionel Messi and Andres Iniesta who can just kill you.
"I would play Fletcher, one more in midfield. I would play Michael Carrick and Ryan Giggs and then Fletcher just doing what he normally does – running everywhere.
"United have a better chance than we have. They have players like Fletcher, [Ji-Sung] Park, [Antonio] Valencia. They are all runners and they can stop players.
"United will be really good because they have the players like Fletcher who will get after them. We played with just Robin van Persie [up top]. I would play with just Rooney, and Valencia and Park just helping when they get the chance to get forward. For most of the game United will be defending.
“You have to get in their faces. We knew we had to stop Messi playing but if you try to stop him too much there are other players who can hurt, you like Iniesta and Xavi. Messi is the best player in the world and you have to stay tight to him.
“You have to talk to each other. Messi likes to drop off and, if he does, you have to go with him. If you give him time to turn and run at you, he can kill you.”
Having beaten Barcelona with Arsenal 2-1 at the Emirates this season, Wilshere says the key is to play high up the field against Pep Guardiola's men.
“We showed it in the second half at the Emirates,’’ he added. “I don’t think they get tired but they seem to ease off in the second half and you really have to go for them.
"The idea was to get around them with three men and press them quite high. They like to play it and if you can nick it in their half you’ve got more of a chance.”
He added: “I’d seen them play against us the year before at the Emirates and everyone kept saying, 'you have to defend or you’re not going to get near them’. I thought 'it can’t be that bad’. But for that first 20 minutes I don’t think I’d ever run so far in my life. The first half, they could have killed us.”
Wilshere also admitted he was too nervous to ask Lionel Messi for his shirt after the match, adding: “I swapped shirts with Xavi and then I asked Cesc [Fabregas] to get me Messi’s. I was a bit embarrassed, to be honest.
"I didn’t want to walk into their dressing room and ask for it.”
The midfielder also said that Barca are capable of influencing a referee's decision during a match, before tipping the Catalans to beat Manchester United.
“We saw it against Real Madrid and they are good at that,’’ he said. “Like Man U, they are good at getting round the referee and convincing him to be on their side.
"I don’t think they are really divers. They are just good at getting round the referee and helping him change his decision. Against us, Sergio Busquets was the main one doing that.”
He added: “I think it will be Barcelona [who win] because of the way they play. It’s the way Arsenal play and the way I like so if anyone deserves to win it’s Barcelona.”