Pep Guardiola admits he does not know what to say to his Manchester City players to stop Lionel Messi.
City face a stern test of their Champions League credentials, and their progress under Guardiola, as they take on the Catalan's former club at the Nou Camp on Wednesday night.
With winning 14 trophies in four glorious seasons in charge of Barca, Guardiola is well aware of just how ruthless the reigning Spanish champions - with the ever-dangerous Messi at their heart - can be.
Asked about Messi at his pre-match press conference, Guardiola said: "I don't know what instructions I can give the players to control the talent.
"Ninety minutes is a long time. They will have a moment and they are so precise. They don't need to create a lot of chances to score a goal.
"It is a good test for us, to know our level against - for me - the best team."
Guardiola has already signed goalkeeper Claudio Bravo from his old club since taking charge at City but he was irritated by a suggestion he tried to tempt more Barca players to move to the Etihad Stadium.
Interestingly, however, he did not completely dismiss the suggestion that Messi may one day want to play in England.
He said: "If you are talking about this summer, I never called Messi. I never called Neymar, Luis Suarez, (Sergio) Busquets, (Andres) Iniesta - I didn't call anybody.
"In the case of Leo I really wish him to play here and finish his career here - play here for a long time.
"But maybe he will think, 'Okay I want to go play somewhere else' because maybe he wants his kids to speak English or live a different experience, like happened to many of us.
"Maybe it could happen, but if he decides to go and it happens, there would be a list of seven or eight clubs that would want to sign him, and it would be down to him. Messi will decide where to go."
Defender Pablo Zabaleta is well aware of the size of the challenge facing City.
He said: "You need to perform at the same level - you cannot make mistakes and you must take opportunities.
"You need a perfect game to beat Barcelona, that is the key. You don't win here easily. There will be moments you will suffer - hopefully not too much."
The match not only pits Guardiola against a brilliant team he helped assemble but a manager, Luis Enrique, who is both a friend and a former team-mate.
Enrique is now building a fine legacy for himself having won two LaLiga titles and the Champions League in just over two years in charge, and he is relishing the contest.
Enrique said: "I was lucky enough to play alongside Pep and share a dressing room with him for Barcelona and the Spanish national team.
"It's a great privilege to do the same thing as managers at the top level and try to overcome that challenge. It's even better to try and win games against friends."