Jose Mourinho is the best coach in world football, his former colleague Aitor Karanka has claimed.
Middlesbrough manager Karanka worked with new Manchester United boss Mourinho at Real Madrid and the Spaniard described their time together as an experience "money can't buy".
Karanka will meet Mourinho's United in the Premier League next season and the 42-year-old explained what he has learned from the Portuguese.
"With Mourinho I learned the value of honesty; the need to explain what was best for the team," Karanka told Marca.
"Sometimes coaches tell you what you want to hear but over time you realise that it's not real.
"With him I learned to say what you thought for the good of the team."
Karanka is now planning for the new Premier League season and he insisted there is no residual tension from his walkout ahead of a Championship game against Charlton Athletic in March.
"That point in time shows you everything," Karanka said.
"I don't think there is a coach who, with a poor relationship with their players, wins six games and draws the last four to be able to win promotion to the Premier League.
"In the final game of the season, we had six players who were already there when I arrived. With all of them there is a more personal relationship now that has helped me to improve."