Jürgen Klopp will not have to wait long before finding his way into the record books this season: all the 47-year-old has to do is to turn up for Borussia Dortmund's first Bundesliga game against Bayer Leverkusen on 23 August. On that day Klopp will become the longest-serving manager in the history of the Black and Yellows and supersede Ottmar Hitzfeld, who was in charge from 1991 to 1997.

Seven years into his reign at the Signal Iduna Park, the Stuttgart-born heavy metal aficionado has become a legend in his own right; a coach whose transformative effect on his club is rivalled only by that of Alex Ferguson, Arsène Wenger and José Mourinho in the modern era. Dortmund were labouring under crippling debt in mid-table and turning over €107m, when "Kloppo" took over in 2008-09. One league title (2011), one double (2012) and three runs in the Champions League later, BVB are debt free, well-liked beyond the German borders for their energetic attacking football and benefiting from revenue well north of €300m per season. And in Mats Hummels, Roman Weidenfeller, Kevin Grosskreutz, Erik Durm and Matthias Ginter, they now have five reigning world champions to boot.

Asked whether he would find it difficult to motivate those players after their triumph in Brazil, Klopp joked that the real problem was the other way around. "It's much worse that genuine World Cup winners will be coached by me for the first time," he told reporters at Dortmund's Swiss training camp in Bad Ragaz.

Klopp has cut a very relaxed figure in pre-season, in contrast to his prickly demeanour half-way through the previous campaign. A series of on-air spats with TV journalists and thin-skinned impatience with reporters in press conferences had given rise to the feeling that he was frustrated with Dortmund hitting the glass ceiling well below Bayern Munich, who finished league champions with a couple of months to spare for the second season running. It was a fundamental misreading of the situation.

The manager and the Borussia board still measure success by how far they have come in a short space of time, not how far they still have to go to become the Bavarian giants' true equals. Klopp's nervousness in the winter months was motivated only by the fear of missing out in the Champions League after inconsistent results and a series of injuries. His speech after the unfortunate 2-0 DFB Cup final defeat by Pep Guardiola's side in Berlin in May ("others only celebrate when they win titles, we are different") was a forceful, defiant plea for perspective. "We played a cup final without seven players who were in the starting XI for the Champions League final a year before, and we came second in the league because the team overcame all problems in exemplary fashion," he said. "Why should we question everything now?"

Why indeed? The chances that the relationship between Klopp and the club will be beset by a seven-year itch remain as slim as ever, as long as Dortmund continue on their carefully planned course of sporting and financial consolidation. "We want to establish ourselves further at the top of the league and qualify directly for the Champions League," said the sporting director, Michael Zorc, the quiet co-architect of BVB's renaissance. "Apart from that we want to get to the final of the cup in Berlin again and make it to the knockout round in the Champions League." It's a relatively modest mission statement, even if Klopp has vowed to approach the coming season with "maximum ambition" after two seasons without a meaningful trophy.

Incessant rumours about the possible defection of Klopp and some of his star players, such as Hummels, Marco Reus and Ilkay Gündogan to the Premier League have been met with a mixture of bemusement and irritation in Westphalia. The manager quipped that he would "eat a broomstick" if Hummels, 25, the elegant centre-back, joined Manchester United this season. He is seen as the face of the club and could be the next captain. and stands as a strong candidate for the captaincy after Sebastian Kehl, 34, stepped down from the position. There is less certainty about the future of the winger Marco Reus, 25 – he has a €35m release clause that becomes active in the summer next year – but on and off the record club officials have insisted he will not be sold this month. "Dear lord, please give them brains and some maths tutoring," the Dortmund press officer, Sascha Fligge, wrote on his Facebook page in response to last week's reports in UK newspapers about Dortmund weighing up an offer from Liverpool. (The message has since been deleted).

Borussia's policy since 2011 has been to let only one key player leave each season. In striker Robert Lewandowski they have arguably lost the most important part of the jigsaw, to Bayern. New signings Ciro Immobile (€18.5m, Torino) and Adrian Ramos (€9m, Hertha BSC) have been brought in to fill the void, possibly in a partnership. Klopp is reportedly thinking about a return to the 4-4-2 system he employed in his early days at Dortmund. His bigger concern, though, seems to be the defence as they conceded 38 goals in the league. "We need to concentrate on conceding fewer times next season," he said in Bad Ragaz. Otherwise business as usual is Klopp's promise. "Only stupid people are changed by success," he said in reference to his world champions. "But if a player comes back from the World Cup with a view to doing things differently, I'd listen to him and then probably carry on as before."