AITOR KARANKA believes promotion back to the Premier League has proven that chairman Steve Gibson was right to invest in English experience last season.

Boro are planning for a first top-flight campaign since 2009 and work is already underway to strengthen the squad.

Karanka and his recruitment team are looking to Europe for players, believing there is greater value for money out there; like the £3.8m paid to Ajax for Viktor Fischer, while they have landed defender Bernando Espinosa as a free agent.

But Karanka knows the importance of having players with Premier League pedigree, claiming it was important for him to have spent £12m on Jordan Rhodes and £4m on David Nugent last season to boost the attack. They also signed Stewart Downing for £7m.

“Sometimes you think you have good players that seem cheap but in the end they don’t engage [with the style of football] … they’re in and out, which is expensive,” Karanka said.

“[Rhodes] and Nugent guaranteed goals, they knew everything. We needed to spend those amounts because we knew we would get goals which, ultimately, helps you achieve promotion.”

In his interview with Marca, the Middlesbrough boss reiterated how his work with Jose Mourinho at Real Madrid was invaluable. The pair will go head-to-head in the Premier League next season after Mourinho's appointment at Manchester United.

“With Mourinho I learned the value of honesty,” he said. "The need to explain what was best for the team. Sometimes coaches tell you what you want to hear, over time you realise that it’s not real. With him I learned to say what you thought for the good of the team.”

That level of honesty caused a few problems in the Middlesbrough dressing room last season, culminating in things coming to a head before the trip to Charlton in March when Karanka was told to stay away.

However, after a meeting with Gibson he remained in charge and the decision was vindicated by the fact they went on to celebrate promotion.

“That point in time shows you everything,” he 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.”

Boro are set to return to Karanka’s favourite training base in Marbella later this summer, with a behind-closed-doors friendly with Real Betis.

Karanka tends to take his squad to Marbella’s Football Center and has already had them there four times since taking over.