Lucas Moura believes Paris Saint-Germain can get the better of Barcelona, but joked there is no way they can stop Lionel Messi without breaking the rules of the game.
The Ligue 1 champions host the Catalan side for the first leg of their Champions League round-of-16 tie on Tuesday, off the back of a 3-0 win over Bordeaux on Friday.
PSG are currently on a four-game winning streak, but Barca are unbeaten in 11 and have won eight of those, and Lucas believes the hosts are the underdogs. With the free-scoring Messi in their ranks, the Brazilian feels Luis Enrique's charges have a threat who cannot be contained without the help of some rope.
"No team is unbeatable, but of course for me they are the favorites," he told AP. "They are the best team in the world, you have to respect them.
"For me it's impossible to stop [Messi]. You have to tie him up.
"The tactic is to prevent the ball getting to him. You must be very, very organised."
Lucas, 23, also pointed to the attacking danger posed by his compatriot Neymar, who has 10 goals and 15 assists in 28 appearances in all competitions this season.
"It's great for our country to see him doing well there, and me doing well here," he said. "He's a great example. I'm happy for him, for everything he's doing there and in the national team as well.
"I don't think he can be like Messi, because every player has their own style and their own history. But I think that, after Messi, he can become a great, great player as well and write a great history for Barcelona."
Lucas, meanwhile, remains key for PSG, having scored 14 goals in 34 appearances across all competitions.