This article is part of the Guardian's Euro 2012 Experts' Network, a co-operation between 16 of the best media organisations from the countries who have qualified for the finals in Poland and Ukraine. guardian.co.uk is running previews from two countries each day in the runup to the tournament kicking off on 8 June.

It was during the 2006 World Cup that people around the globe got to see Germany in a new light. The sun shone for weeks from an almost cloudless sky, the country's population was in a joyful party mood and the Germany team played wonderfully, yet ultimately without success – if you're minded, that is, to regard third place in a World Cup on home soil as a lack of success.

In short, the Germans, their weather and their footballers behaved completely opposite to the way they're often said to behave. And nothing fitted better into the easy-going mood of this summer fairytale than "Schweini and Poldi" with their boyish charm. Bastian Schweinsteiger and Lukas Podolski: the magic of 2006 made them appear heroes of a new, uninhibited Germany, like two playground pals in football heaven.

When the Germany squad take their place this summer as one of the tournament favourites at Euro 2012 in Poland and Ukraine, Schweinsteiger and Podolski, now both 27, will be there. However, their roles and their importance within the team have changed in very different ways. While Schweinsteiger – a certain Mesut Ozil aside – is the undisputed maestro in the Germany midfield, Podolski isnow allowed no more than a bit-part role as the player with the strong left foot has to fight off strong competition in his position from André Schürrle of Bayer Leverkusen.

To watch Podolski in training is to understand what kind of a person he is. He loves it. There has not been much to laugh about recently at Köln but Podolski is someone who has a cheerful demeanour even in difficult situations. Like a proud racehorse, he skips around the group of players. He teases team-mates, he hits difficult, raking passes to them and grins impishly if anyone has difficulty controlling the ball. The cheeky smile, the thumbs-up, his dynamic running game, the slightly pulled-in shoulders, the arms held up high – trademark Poldi.

When he was young, his parents never had to worry about him. If he was late coming home, everyone on the street knew where he was: in the park playing football. As a professional, too, Podolski gives the impression that during the game he forgets about everything away from the pitch. It almost feels as if nothing has changed and that after training he will, just as he used to do in his hometown of Bergheim, jump on his bike and cycle home with the ball in his saddlebag. Podolski says: "When I'm on the pitch I'm happy. I can shut everything else out. Football is like recreation for me. I'd sooner be playing five-a-side than going out to eat or shopping."

It seemed as if nothing could stop him. After the 2006 World Cup, the best young player of the tournament moved from his childhood club, Köln, to Bayern Munich, where he hoped to take the next step towards becoming a world star alongside his friend from the national team, Schweinsteiger. However, the effortless ease of his first few years as a professional at Köln – where as the local lad he had triggered a wave of hysteria – did not follow him to Munich. In his first season there he lost his way, got injured and cut himself off from Munich. He lived in the quiet village of Hechendorf am Pilsensee, far away from the big city on the Isar. "By doing that, Lukas never really got to know the Munich mentality," Schweinsteiger has said.

Nevertheless, when Jürgen Klinsmann became Bayern manager, Podolski's fortunes appeared to be looking up. All seemed set for a return of the fairytale trio of 2006: Schweini, Poldi and Klinsi. But it did not turn out that way. Immediately after joining Bayern, Klinsmann sat down and told Podolski that he regarded him only as third-choice striker, behind Miroslav Klose and Luca Toni. Why that was, Podolski has never been told. The days of life being a walk in the park were now well and truly over. Podolski's verdict on his time with Bayern is mixed: "I gained a lot of experience and did win some medals, but I was given too little playing time. Instead, whenever I did get on the pitch for 10 minutes a big thing was made of it. And if I didn't manage a shot on goal, everyone immediately said: 'Lukas has lost it.' If that carries on for a while then it is quite difficult for a footballer. Then you lose a little bit of enjoyment. When I see the current Bayern team I sometimes ask myself whether I couldn't have fitted in there, but that is in the past now.

"It was hard every time I found out that I was not in the starting XI. But over the week that frustration gradually disappeared in training." In 2009, he returned to his beloved home, to Köln, who had been scrapping to avoid relegation for the previous few seasons. It was therefore no surprise that within the hierarchy of the national team he gradually dropped down the pecking order. After the Euros, Lukas Podolski will move to Arsenal. Whether he can make his mark at a club of such calibre is something he has yet to prove.

The past six years have not always been plain sailing for Schweinsteiger either. After the 2006 World Cup he seemed to have ensconced himself in his comfortable life at Bayern. His agent, Robert Schneider, says: "A good player already earns a lot of money at Bayern early on. That was perhaps what the chairman, Uli Hoeness, was alluding to when he talked about Bastian always having had things too easy." Schweinsteiger was a regular starter at Bayern, but other players were pulling the strings. The image of the prankster Schweini, which had helped him and Podolski to achieve nationwide popularity at breakneck speed, now became a curse. It was an image of a footballer who did not want to grow up.

His friendship with Podolski was apparently never really as close as it was made out. However, one common bond between them is that in 2009 they both started to rethink their careers. After an unsuccessful time in Munich, Podolski decided to return home to Cologne and to accept his fate as the carnival city's prince. Schweinsteiger, on the other hand, decided to knuckle down in order to become the natural successor to Michael Ballack. He was helped in this pursuit by no longer having to play out of position on the wing. He had started out wide and every new Bayern manager had overlooked his talents or thought he had better players for the more central roles. It was not until Louis van Gaal drew a small arrow on his tactics board that Schweinsteiger's career again took a major leap forward.

In tandem with this and in contrast to Podolski he gave up the role of mischief maker. Schweinsteiger is now one of the inner circle of senior players at Bayern and with the national side. He was one of the leading players who did not want a public reception in Berlin after the 2010 World Cup, because he did not want the team to be celebrated for finishing third. "I've come third in the World Cup before, so I wasn't all that ecstatic. There eventually comes a time when I need to start winning international titles as well," he said. To emphasise the point, he added: "I don't want to win 20 doubles and then retire without having won a major trophy with Germany. I just don't want to."

It seems as if, along with his Bayern colleague Philipp Lahm, he is now acting as a kind of mentor, helping to bring along the next generation of players such as Mesut Ozil, Thomas Müller and Sami Khedira. "When you keep producing high-level performances you can get more and more responsible," he says. "That is the case in every job, isn't it, the fact that it is easier to share your experiences after a few years.

"The fact that my manager at Bayern played me where I can perform at my best [in central midfield] speeded things up. And then I become third captain of Bayern and vice-captain of the German national side. Now I would like to think that I can help the younger players coming through. I know from my own experiences that they may fall into a little hole at some stage of their career. And then they need to show how quickly they can get out of that hole and maybe I can help them with that."

Schweinsteiger has fallen into a few holes himself. Getting sent off at Euro 2008 against Croatia was a low – Germany lost the group game 2-1 – and being booed at a meeting with the Bayern fans in November 2009 also hit him hard. "All three captains were at that meeting and when Mark van Bommel and Philipp Lahm were called out all the fans cheered but then when my name was called out they whistled. That was hard. Now everyone is cheering me but for a year I was whistled by my own fans. My own fans, for whom I have always given my best. I will always remember that moment because it showed me that in football you can rise to the top quickly but you can also fall right down very quickly."

That scenario seems very unlikely for Schweinsteiger at the moment, even despite his critical penalty shootout miss in the galling Champions League final defeat to Chelsea. As he keeps improving on the pitch, his reputation off it is also changing. For some time now, Schweinsteiger has asked to be called by his full name. According to some reports, Germany's biggest tabloid newspaper, Bild, is said to have done a deal with Schweinsteiger's management team not to refer to him as Schweini any more. It is not serious enough. "At the start of my career that nickname helped me a lot," he says. "But everyone moves on. I'm a different person now." Podolski still has yet to prove he has moved on from Poldi.

Tim Jürgens writes for the German football magazine 11Freunde

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