Abelardo Fernandez has said his friendship with Barcelona counterpart Luis Enrique will not affect things when his Sporting Gijon side face a team he called "maybe the best of all time."
The two were in the same Gijon team as eight-years-olds, later breaking through into the first team at the same time before becoming Barcelona and Spain colleagues.
On Wednesday, they meet as coaches for the first time at El Molinon in a game that could see Barcelona stretch their lead at the top of La Liga to six points.
Abelardo told his prematch news conference: "When we were little, we never thought we were going to play for Real Madrid, Barcelona or the Spanish national team.
"We are friends, but during the game Luis will defend interests of Barcelona and me those of Sporting. Nobody should think that [Lionel] Messi and company will have the red carpet rolled out for them. We will make things difficult for them.
"It is tough to do them damage, not just for Sporting but for all teams. It's the best team in the world -- maybe of all time."
The game also sees Sporting playmaker Alen Halilovic, on a season-long loan from Barcelona, face his parent club, and he told Barca's official website: "I'm very happy to play against Barca.
"It will be a nice game and I'm really excited. My best friend is at Barca -- [Ivan] Rakitic. I really want to play against him but also against Messi, Neymar and Luis Suarez. It is the best team in the world."
Halilovic, 19, who has three goals and four assists in 22 appearances for Sporting this season, said he had not yet thought about where he would be playing next season and added: "We'll see what happens."