Great goalkeepers are hard to come by. The two best, Iker Casillas and Gianluigi Buffon, have split the goalkeeper spot in the FIFA World XI between them for the past seven years.
The next likely candidates to upset their duopoly are around 25 years old now, the likes of Manuel Neuer and Joe Hart may one day become the best in the world, but neither is likely to challenge Casillas or Buffon just now.
The elite group of great goalkeepers is exceptionally small then. Top clubs compete for slim pickings when it comes to truly world class shot-stoppers.
Manchester United recently spent £17m on David De Gea as they looked to nail down their number one jersey, but if the experience of the Spaniard at Old Trafford shows one thing, it's that experience is awful valuable at the goalkeeping position.
Sir Alex Ferguson hopes De Gea goes onto become one of the world's best. The 22-year-old has time on his side, and he may still fulfil his considerable potential, but there's already a next generation of young keepers ready.
Barcelona, according to recent reports, have put together a list of young goalkeepers to replace veteran shot-stopper Victor Valdes, and are looking to the next crop. Some of the names mentioned include Vicente Guaita of Valencia and Roma's Maarten Stekelenburg - two players who don't make it onto this this. But some, including two German stoppers, do make Barca's reported 'shortlist', and they're both great keepers.
So, GMF looks at five of the best, each 20 years old or younger. Which do you think will go on to become the next Casillas, the next great goalkeeper?
Have your say by joining the debate in the comment box below...
Marc-Andre ter Stegen - Borussia Moenchengladbach
The 20-year-old Borussia Moenchengladbach is one of the most highly-rated young keepers in a Bundesliga full of them.
Already capped by Germany, ter Stegen is just one part of a hugely talented young German generation. The 20-year-old first got his run in the time back in 2010, helping Moenchengladbach to avoid relegation, before cementing his place in the first-team in the following season.
Bernd Leno - Bayer Leverkusen
The youngest German goalkeeper ever to play in a Champions League match got his big break on loan at Bayer Leverkusen. Stuttgart couldn't see the potential, and eventually let Leno join the Westphalian giants on a permanent basis in 2011. A big mistake.
Like ter Stagen, Leno has progressed through the German youth ranks, playing at every international age level from under-17 through to under-21. The 20-year-old is yet to make his full national team debut, but he's got plenty of time.
Manuel Neuer, Bernd Leno, Ron-Robert Zieler and Marc-Andre ter Stegen - quite a stable of keepers Joachim Loew can choose from.
Thibaut Courtois - Chelsea
Coutois was signed by Chelsea for around £8m in 2011, and was promptly loaned to Atletico Madrid for the season.
Stepping to David De Gea's shoes was no small task, especially for a 19-year-old Begian under-18 international. But Courtois is a special talent.
His time at the Vicente Caulderon has been hugely successful, one Europa League title and a 4-1 demolition over parent club Chelsea in the UEFA Super Cup has been followed by an impressive second season - Atletico sit second in La Liga, seven points clear of city rivals Real Madrid.
The Belgian 20-year-old now has seven caps for his country, and is widely expected to challenge Petr Cech for a starting berth at Stamford Bridge next season. Barcelona want him, and it's not hard to see why.
Jack Butland - Birmingham
Still just 19-years-old Butland already has an England cap, is established first-choice at his club, and has most of the Premier League watching him. A move is surely only a matter of time for this 6ft 5in stopper, with Liverpool strongly linked.
Strong reflexes, a big frame, and a level headed temperament have made him one of the most sought-after English players in the January transfer window, and he's widely expected to be Joe Hart's main challenger for the Three Lions number one jersey in the next couple of years.
Maxym Koval - Dynamo Kiev
Eastern Europe has a reputation for producing great goalkeepers, and Koval could be the latest.
Aged 16 he made his debut for Metalurh Zaporizhya, and kept a clean sheet. 19 games later, he moved to Dynamo Kiev - the Ukrainian giants were so impressed by his performance against them they made his signing an urgent priority.
With first-choice keeper Oleksandr Shovkovskiy injured, Koval was thrust into the first-team, still just 17-years-old. His performances then, back in 2010, led Spanish football magazine Don Balon to name him as one of the best 100 young players in the world - alongside David De Gea, then of Atletico Madrid.
Shovkovskiy picked up another injury prior to Euro 2012, and once again Koval filled in, playing the final three games of the season. Shovkosvskiy has since returned to the first-team, but the number one jersey is now occupied by Koval. A huge talent, with experience of continential competition in the Europa League and a Ukraine cap under his belt already.
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