Former Middlesbrough boss Aitor Karanka has spoken of his time as Real Madrid assistant coach to Jose Mourinho.

Karanka has no doubt the Manchester United manager laid the foundations for the current success.

He told Marca: "The picture in Madrid has changed a lot. Jose arrived to compete with a Barcelona team who were almost unstoppable, and we managed to compete with them. We did not win any Champions Leagues, but we were close.

"Mourinho's winning mentality put the club back into a competitive environment."

On the prospect of Mourinho returning, Karanka added: "It's complicated. The years have gone by, Zidane is doing well and Jose has won three titles in his first year at Manchester United... but you never know."