It is hard to define Lothar Matthäus. A box-to-box midfielder or a libero? Germany’s most-capped player but perhaps still a little unloved? Exceptional in the air but only 5ft 9in tall. A Bayern Munich legend who probably played his best club football at Internazionale. The ultimate team player but with arrogance and an ego that all the greats of the game seem to possess. How well he fits into an interview series about 1990s footballers could even be questioned, given his career spanned four decades, but it is his highest and lowest moments that bookend the 90s, captaining West Germany to World Cup glory in 1990 and watching on as Bayern capitulated to Manchester United in 1999, almost exactly 20 years ago to the day. In perfect English, he speaks quickly and agitatedly, as though the clock at the Camp Nou is still ticking.

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“We were the better team on the day, but we lost concentration,” says Matthäus of that Champions League final. “Maybe it was too easy for us in the 90 minutes. We controlled the game, but we didn’t score the second.” He laughs, and it is all too obvious that this still smarts.

With Bayern leading 1-0 and dominating, Matthäus had taken himself off on 80 minutes, exhausted but satisfied. At 38, he was still one of the world’s best, winning German Footballer of the Year that season. Having mastered a defensive libero role for the previous few years to prolong his career, he was deployed back in midfield against United, whom he dominated in the absence of the suspended Roy Keane and Paul Scholes.

“In this game I played in the middle against [David] Beckham and after 80 minutes I was tired,” Matthäus explains. “Different runs, a different speed than when I played sweeper. I don’t know how much they missed me, when I went off. Maybe the change was wrong.”

Facebook Twitter Pinterest Lothar Matthäus talks with David Beckham after the final whistle of the 1999 Champions League final. Photograph: Tom Jenkins/The Guardian

Bayern’s collapse and two injury-time goals for United suggest the substitution was indeed a mistake, but Matthäus’s ability to make decisions for the team over personal pride or glory was a quality that underpinned his career, and often went unnoticed.

A similar situation arose late in the 1990 World Cup final, and this time rather than being a question of fatigue, it was over whether Matthäus – West Germany’s designated penalty taker – should take the decisive 85th-minute spot-kick. That time, he made the right call.

“My right boot had broke in the first half against Argentina,” Matthäus explains. “I changed them at half-time to a completely different type, but they felt so unnatural in the second half. So I said to Andreas [Brehme]: ‘I don’t feel safe, please go and score the penalty.’ Our manager, Franz Beckenbauer, told to me many times: ‘Don’t ask me when you see something on the field. Do what you think is best.’”

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Brehme obliged and Matthäus lifted the World Cup as captain, but it fascinating that his mental approach allowed him to detach himself from such a high-pressure situation and choose the most logical option. Log on to Matthäus’s website, and the first words that greet you are “Persistence, perfection”, with the tagline “for success, there are no compromises”. It encapsulates Matthäus. What is more, unlike a tired motivational slogan painted across the wall of a dressing room, reading his words you believe them and his pursuit of something greater. It was this force of personality that convinced Bayern’s manager, Ottmar Hitzfeld, to agree to the substitution in 1999 and gave Brehme the confidence to take that kick in 1990. Defeat and victory are linked by the same thread.

In England, 1990 is largely remembered for the semi-final defeat, Gazza’s tears and the shootout woe. As West Germany’s players celebrated Chris Waddle’s wild miss, deliriously piling on to goalkeeper Bodo Illgner, it was also telling that it was Matthäus who first embraced and consoled the man from Gateshead.

Facebook Twitter Pinterest Chris Waddle is consoled by Lothar Matthäus after his miss in the 1990 World Cup semi-final penalty shootout. Photograph: Bob Thomas/Getty Images

“Waddle was one of the best players for England and I respected him,” says Matthäus. “I’m sure I cannot help him but for me it was a normal reaction, to go to him. I told him I was sorry and that I knew the feeling because I missed a very important penalty in the cup final in 1984.”

That DFB-Pokal final defeat had been Matthäus’s final match for his boyhood club Borussia Mönchengladbach before he joined the victors, Bayern. But the transfer was nearly scuppered for sponsorship reasons. Matthäus grew up in the small Bavarian town of Herzogenaurach, where Puma and Adidas were founded by the Dassler brothers and where the sports companies continue to be based today.

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“All my family worked for Puma,” says Matthäus. “My mother worked there and my father was the guy that opened and closed up in the evening. We lived in the neighbouring building – just a couple of steps and I would be in the Puma factory. All 300 people that worked there knew me; it was my adventure playground. I knew everything, even how to make a shoe sole.

“At that time players were only allowed to play for Mönchengladbach in Puma boots and only allowed to play for Bayern in Adidas. So when I met Bayern for talks, they had to go and talk with the owner of Adidas and said: ‘Look we have a chance to get Lothar in our team, but he has to play with Puma.’ Because they were from my village, they eventually gave Bayern the permission for me to play in Puma boots.”

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The German Football Federation, sponsored by Adidas, was not so forthcoming at international level but there was no such trouble at Internazionale, whom he joined in 1988 after three Bundesliga titles with Bayern. Winning the Scudetto in his first season and the inaugural Fifa World Player of the Year in 1991 he was pitted against Napoli’s Diego Maradona, who described Matthäus in his autobiography as “the best rival I’ve ever had”. The two would also battle fiercely on the international stage, trading blows in the 1986 and 1990 World Cup finals.

“I’m sorry that Diego is not now in the best condition but I still respect him,” says Matthäus. “He’s maybe lost a little bit of himself but I’m always happy when I see him. He was the best player and it’s not nice to see him in this situation. I hope he will find a better way. Maybe he is happy, maybe he will change a little bit. When I saw him last year in Russia, I was surprised how he has changed. It’s not nice.”

Facebook Twitter Pinterest Lothar Matthäus met Russia’s president Vladimir Putin at last summer’s World Cup. Photograph: Alexei Druzhinin/Pool/Tass

Despite Germany’s group-stage exit, Matthäus has happy memories of last summer’s tournament. “I know Vladimir Putin from London 2012,” he says. “Putin speaks very good German and we talked about football and judo, the best restaurants and the Brexit, American politics and Russian politics. My wife is from Russia. I like the country, the mentality of the people.”

These days Matthäus is a pundit and an ambassador for Bayern, and he will again line up alongside Stefan Effenberg, Mario Basler and Sammy Kuffour against a Manchester United team containing Beckham, Ole Gunnar Solskjær and co in a charity match at Old Trafford on Sunday, to mark the 20th anniversary of that famous final. “I am happy to see the players again,” says Matthäus. “Sure, 1999 was the worst moment for me, but I have to congratulate Manchester United. Football is not only sunshine.”