It must be a peculiar feeling for Iker Casillas to feel like an old crony. Here is the player who for the best part of a decade was one of football's great exceptions. In a position so specialist, so scrutinised, that experience and proven ability to handle the pressure is preferred, the boy from Madrid was an anomaly. There was, in every sense, very little he could not handle even in his teens.

Casillas became first-choice goalkeeper at the most glamorous club of its time aged 17. He was the youngest goalkeeper to win the Champions League when he kept a clean sheet as his team trounced Valencia 3-0 a few days after his 19th birthday. He won it again at 21 (to put that into perspective, the average age of all goalkeepers in the Champions League final since then is 31). He captained his country to a European Championship and World Cup while in his 20s. So prodigious has his career been he was perfectly entitled to have a mid-life crisis last May when he glanced in the mirror at his 30-year-old self.

Now, scanning the Champions League, there are an increasing number of clubs who are trusting in youth in this most demanding of roles. When Manchester United turned to the 20-year-old Spaniard David de Gea to take over from the years of goalkeeping wisdom personified in Edwin van der Sar the questions were more about temperament than technique.

De Gea is settling, though, and if he is picked for this week's European assignment, he will come up against another bright young keeper. FC Basel's Yann Sommer is 22. The pair competed in the final of the Under-21 European Championship in June, having sparkled throughout the tournament.

In the same competition two years ago England met Germany in the final. In goal for Germany stood a giant who was not short of confidence: Manuel Neuer. A frustrated onlooker for England was Joe Hart, who was suspended for the final. Both keepers have grown in stature since, and now hold the full international jersey as well as playing for clubs who can aspire to winning the Champions League. They also meet this week, as Manchester City travel to Bayern Munich on Tuesday for a duel that promises to fascinate.

Not so long ago Neuer, at 25, would have been considered just about old enough to be reaching goalkeeping maturity. Few who witnessed his extensive repertoire in Schalke's colours last season to deter Manchester United would dare to question his qualities. But it has been an eventful few months for the son of Gelsenkirchen. His transfer to Bayern was unusual in that it was not only the supporters he was abandoning who felt aggrieved, but also those he was set to join. Even when the move was merely speculated, and Neuer was a visiting player at the Allianz Arena, Bayern's fans jeered him relentlessly and hoisted banners rejecting him so vehemently that the chief executive, Karl-Heinz Rummenigge, felt obliged to apologise afterwards on television.

In pre-season, a group of Bayern ultras continued the campaign against their expensive, newly signed keeper. The club duly felt moved to make these fans persona non grata. A month later, Neuer made his competitive debut in front of a full home crowd. If it was hoped that would end the coolness towards him, the outcome was rather unfortunate. A calamitous mix-up between him and the new defender Jérôme Boateng gifted the game to Borussia Mönchengladbach. In the words of the legendary Oliver Kahn, "he goofed, but the same as any player of FC Bayern, he needs your support".

The misery has lifted, however. Neuer has not conceded a goal since. Nine consecutive clean sheets, which included a hostile return to his former disciples at Schalke, have given him a firm foundation. He has discovered, though, that a goalkeeper's life with Bayern has a totally different emphasis from what he was used to.

Opportunities to shine are limited. Kahn used to often mention how the club requires its keepers to be as good at concentrating as the nuts and bolts of resisting shots and crosses. "Games in which I've got nothing to do are difficult," Neuer concedes. Süddeutsche Zeitung sniggered that he was "the best-paid unemployed person in the world".

Notably, the media made a fuss of another young keeper who was busy in the last round of the Champions League. Bernd Leno was the toast of Germany for his resistance in the face of Chelsea for Bayer Leverkusen at the age of 19. He is such a highly regarded talent, the critics are beginning to wonder if there might not soon be some serious competition for Neuer in the German national team.

The growing list of Europe's young goalkeepers, with the likes of Arsenal's 21-year-old Wojciech Szczesny another who looks to be one of his team's most potent weapons despite his age, suggests something behind the scenes has changed.

Are goalkeepers growing up earlier than they used to? Are they better educated? Do they go through specific preparations designed to help them absorb pressure younger? Are they simply more talented than the generation they are replacing?

We in England may well scratch our heads. The answer probably lies in Germany, where 16 of the 18 Bundesliga clubs have a domestic player in goal. The Premier League's current rate? Just four out of 20.