One of us will be happier than the other, says Aitor Karanka as he faces friend Jose Mourinho

Karanka will take on his mentor for the first time tomorrow when Boro arrive at Old Trafford looking to end United’s five-game winning streak.

The pair may be at war for 90 minutes as they attempt to get the better of each other, but the friendship they forged at Real Madrid, where Karanka served as the former Chelsea manager’s No 2 for three years, will survive the white heat of battle.

Mourinho’s mind games off the pitch and his antics on the sidelines paint a picture of huge intensity, but as a man who knows him better than most, the Boro boss insists there is more to the Portuguese than meets the eye.

Asked if he is different away from football, Karanka said with a smile: “A little bit. Yes, he’s different. He’s different because it is impossible to live 24 hours with that pressure, with that tension that he puts into every single training session or every single game.

“He is different. We are really good friends and we have a really good relationship. But it’s football, it’s 90 minutes, so for 90 minutes, you can’t be friends.

“At the end of the game, we will have a glass of wine, a beer or a Coke and one of us will be happier than the other.”

Karanka is working on a plan that may include a surprise, but added: “I’ll try – but it’s difficult to surprise Jose.”