Andres Iniesta: Immortal, but no longer invincible?

"It's not as if football is now a science, and that playing it this way means you will always win," says Andres Iniesta of the distinctive style that has led to Barcelona and Spain being considered by some the greatest club and country sides of all time. The boy who grew up with Michael Laudrup posters on his wall, who debuted alongside Juan Roman Riquelme and who, with a style that evokes both players, has won 19 trophies in 10 years, knows that time does not stand back admiring... it marches on.

Barcelona had not lost away in the group stages of the Champions League for six years until they visited Celtic this week. Three weeks ago Spain failed to beat France, thus ending a run of 24 straight qualifying victories. It may seem like sacrilege to ask if these two great teams have peaked, but that mesmerising first 45 minutes against Italy, when Spain became the first team to win two European Championships either side of a World Cup, could be the height from which they will now gently fall.

"It was the most complete match we played," says Iniesta of that night in the Olympic Stadium in Kiev. "We got the goal early and played the ball so quickly with speed and aggression. But we know that between now and two years' time we will need to improve if we are to win again. Everything that has gone before will count for nothing."

Reputations counted for nothing on Wednesday when Celtic beat Barça. And France not only drew with Spain in Madrid last month, they dominated them. What there is no shortage of, says Iniesta, is a desire to go on winning.

"The secret of sustained success is that there is always something new," he says. "In Poland and Ukraine it was doing what nobody had done before. Now there is the chance to win the World Cup in Brazil: what more of a challenge could there be? A Brazil finals is unique; it is a massive extra in terms of motivation. Maybe after winning two Euros and a World Cup you would think there would be nothing else to strive for; then this comes along. It's a gift."

For a long time now Spain and Barcelona have played without fixed centre-forwards; in the absence of the injured Gerard Pique and Carles Puyol they have also played without orthodox centre-backs. Iniesta eloquently defends the philosophy – and passionately defends the right for other ideas to exist alongside it.

"We play the way we do because it suits us," he says. "If we played any other way we would not have the players to pull it off. It's pragmatic. We believe we have the best chance of winning playing this way but the football that Spain and Barcelona play is not the only kind there is. Counter-attacking football has just as much merit. There are many different styles and variations; that is what makes this such a wonderful sport."

A minority of Barcelona supporters react to their defeats with a religious zeal that condemns the opposition for not beating Barça at their own game – as if anyone can. How dare Celtic defend well and take their chances on the counter-attack? It's Goliath's army complaining that David used a slingshot and a stone.

Iniesta accepts that the Spain and Barcelona way just happens to have dominated football for the last four years so they have earned the right to pontificate a little.

"Without the trophies it would all mean a lot less," he says. "What we have done is prove that it is possible. Euro 2008 showed you could win with a group of players who weren't physically imposing in any way, in fact who were completely the opposite. We showed that, luckily for football, in this sport pure talent can come out on top of the purely physical."

Spain were the smallest team in Poland and Ukraine, Barcelona are often the smallest side in the Champions League, something which cost them on Wednesday when Jordi Alba was left marking Celtic's Victor Wanyama at a corner.

The invasion of Spain's "unimposing" midfielders, as Iniesta calls them, has brought Juan Mata, Santi Cazorla and David Silva to England. "There is no rule that says a footballer needs to be 'this high' and 'this wide'," Iniesta says. He and his international team-mates have proved that you can't build the perfect modern footballer, because just when you think he looks like Cristiano Ronaldo someone who looks nothing like Ronaldo is voted European Footballer of the Year.

"To even be stood there between Cristiano and Leo [Messi] was like a prize for me," Iniesta says of the award he picked up in August. That admission fits the nicer-than-nice image that has developed over the years. The former manager Pep Guardiola famously made Iniesta the role model for every tearaway wannabe at Barcelona when he said: "He has no tattoos, no earrings. If young players want to know what to do and how to behave I just tell them to follow Andres."

Does the player begrudge the Goody Two-Shoes image? "It's not about being good or bad," he says. "You're not the bad guy if you've got tattoos and you're not the good guy if you haven't. Some people like you, some people don't. You just have to be yourself and people make their own minds up from that. You have different sorts of people in life, so why should it be any different in football?"

After he signed his first big contract, Iniesta bought a house for his mother and made sure his bricklayer father was able to retire at 40. But he says the soft exterior covers a harder centre without which no one makes it. "If there is one thing that all players have in common it is that winning, competitive gene; the ability to overcome obstacles and fight for what you want from your career. It might look easy to reach the elite and stay there but it isn't and all the players that have achieved those things have that fighting quality. The big ones, the small ones, the good-looking ones, the ugly ones, the nice ones, the not-so-nice ones, they all have that will to succeed."

Iniesta's mental toughness first manifested itself when he stopped crying himself to sleep at night as a 12-year-old boarder at Barcelona's Masia youth camp 300 miles from his family. "You surprise yourself when that cold-blooded desire to make it starts to come through," he says. It served him well later when playing through injury or coming back from long lay-offs.

"In certain definitive moments the human body can defy the limits that would normally apply. In the European Cup final in Rome against Manchester United I was broken, I couldn't shoot with my right leg but I played on and we won.

"The World Cup win came after missing much of the season with injury. When the final whistle blew, instead of thinking 'I'm a world champion', the first thing I thought about was all that suffering."

He describes that goal in Johannesburg as being given the "one last bullet", saying: "I knew we were going to be world champions when the ball came to me; I just had to wait for gravity to do its job." He talks about "hearing a silence" as he drew back his right leg to shoot.

Losing this week brought no real complaints from Barça fans – though it will come if other sides do to Barça as Celtic and Chelsea have now done. There is already criticism for the Spain side at the slightest blip.

"We have earned the right to be judged that way because of the way we have performed and the titles we have won," Iniesta says. "The better you play, the better you're expected to play all the time. When it doesn't happen people start asking questions."

Barça remain favourites to be at Wembley for the Champions League final and Spain will be the team to beat at Brazil 2014. "No one is complaining," Iniesta says. "We wish things had gone that well for the last 50 years, and that the expectations had always been so high."

My other life: As old boots collector

Andres Iniesta still owns the first pair of football boots ever bought for him. The size eight adidas Predators take pride of place alongside Paul Scholes' Manchester United shirt from the 2011 Champions League final and a recording of the radio commentary of his World Cup-winning goal – complete with screams of "Immortal, eternal, Iniesta!"– in a collection of memorabilia at his home in Barcelona and at his grandfather's bar in his hometown of Fuentealbilla. "My father has made a museum with my cuttings and photographs," he says. "I more or less have all the boots I have ever played in."

Pep Guardiola: Where he'll go next

With every stutter from one of England's top four, thoughts turn to the man who has won the European Cup once as a player and twice as a coach. Does Andres Iniesta believe the former Barcelona chief Pep Guardiola could repeat the trick with an English side?

"The one thing I'm sure about is that the day he starts coaching again, whichever team it is that he takes over will have made the right decision in hiring him. As to whether he is able to get his team playing as he wants them to, and get them to feel the same way about the game as he does, that will be down to the players.

"What he achieved [at Barcelona] came from him being able to make us believe in him and believe in his message.

"As a coach he would always ask 'How is the person?' and not just 'How is the player?' He is a players' manager. And, of course, he sees football like nobody else and will always give you solutions out on the pitch."

Iniesta does not believe the coach will break his sabbatical in New York to take a new job in January. Even if he does, their mutual admiration would not draw Iniesta to the Premier League, much as he loves watching it. "My only ambition is to retire at the club that picked me up as a 12-year-old boy and gave everything to me and my family," he says.