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Lluis Gene/AFP/Getty Images Barca's Lionel Messi and Real Sociedad Xabi Prieto are that rare bread in soccer -- the one-club player. Barca's Lionel Messi and Real Sociedad Xabi Prieto are that rare bread in soccer -- the one-club player.

Real Sociedad midfielder Xabi Prieto's steely nerve to bury a penalty against Athletic Bilbao in last weekend's Basque derby -- and his joyous and heartfelt celebration -- was evidence of that rarest of things in modern soccer: a player kissing a club crest to symbolize a team he genuinely cares about, down to the very fiber of his soul.

When Real sunk into Segunda Division at the end of the 2006-2007 season, Prieto, who had broken into the Spain under-21 side the season before, was widely tipped to join the San Sebastian team's noisier neighbor, which was in the Primera Division. It would have been an astute move for his development as a player. But Prieto was no lamb open to the jaws of Bilbao's lions, stating unequivocally that he would never wear the red and white of the eternal foe.

Prieto's loyalty lied with one club only.

The one-club player is a throwback to an unadulterated era in the sport, before players had carte blanche to hold their employers to ransom and demand astronomical salaries. It takes a particular type of player to eschew the riches of the modern game for personal and parochial pride. But for those who choose the path, fleeting victories are more buoyant than a bank balance that could bail out a failing nation.

Although most news these days is about players angling for bigger contracts, the one-club player quietly goes about the business of leading his team on the pitch, and often off it. These players become part of the club's fabric, its legacy.

Players such as Atletico Madrid captain Antonio Lopez, who despite a few appearances for Spain would consider winning the Europa League his career highlight. Or Raul Gonzalez, who was synonymous with Real Madrid's on-field fortunes for 15 years.

It is increasingly difficult to find one-club players in La Liga, but we should celebrate them: David Albelda at Valencia; Santi Cazorla at Villarreal; Joseba Etxeberria, who despite making a handful of appearances for Real Sociedad made the switch to Bilbao, where he spent 15 seasons, playing the last year (2009-2010) of his contract free of charge.

Naturally, it's easier to be a one-club player in a side that requires a balance between leadership, success and the books. Only Barcelona could afford to let Cesc Fabregas, Fran Merida and Xavi Torres slip through the net of its training academy La Masia, as only Real Madrid could allow the likes of Juan Mata and Alvaro Negredo to line up against them.

When Michel, currently leading Getafe, quit as coach of Real Madrid's youth team, Castilla, in 2007 he railed against the club for its lack of interest in bringing through young players to the first team. It's an argument that still rages in Spain, the battle between Cantera (youth set-up) and Cartera (wallet). Michel formed part of the legendary Quinta Del Buitre, with Emilio Butragueno, Miguel Pardeza, Manolo Sanchis, and Rafael Martin Vazquez in a serial title-winning team. All five came through the ranks at Real.

"There are many Matas: Negredo, [Rubén] de la Red, Javi García, [Álvaro] Arbeloa Madrid's cantera has always been interesting, but if they don't get an opportunity, it means something is being done wrong," concluded Michel to the press, as he stalked from the Bernabeu.

A head count last season found over 60 Real Madrid youth team players in La Liga, but only three -- Iker Casillas, Esteban Granero and Alvaro Arbeloa -- currently wear the white shirt.

At Barcelona, meanwhile, 2010 Ballon d'Or aspirants Lionel Messi, Xavi Hernández and Andrés Iniesta are all products of the club's youth system. Messi alone would cost a suitor his 250 million euro buy-out clause at least, and the Argentinean has made plain his intention to end his career in Catalonia. Indeed, Barca is a unique club in La Liga in that it could field a recognized first team entirely of players brought through its youth system.

With Barca's La Masia rightly regarded as the best finishing school in the world, Mourinho's first act as Madrid coach was to run the rule over the Castilla squad for potential first-team recruits. In Real's dead rubber match against Auxerre in the Champions League, Karim Benzema asserted himself as a worthy accomplice to the injured Gonzalo Higuain, but the presence of Alvaro Morata, Pablo Sarabia and David Mateos on the bench redressed Real's reluctance to promote cantera players to some extent. Mourinho, a consummate planner, seems willing to go where no Real coach has dared before him, to the ranks of the rough diamonds.

It may prove to be a mine of success. When Pep Guardiola assumed control of Barca's first team, he had to fight to keep La Masia starlet Pedro Rodriguez, then largely unknown outside of Barcelona's B team but now enshrined as the only player in history to have scored a goal in six club competitions in the same season. The Camp Nou hierarchy was willing then to let the Canarian leave for a song. His price should anyone wish now to prize him from his alma mater? A cool 75 million euros.

Prieto and Real Sociedad met Barca late on Sunday night and despite sitting comfortably in the top 10 in its first season back in La Liga, conceded five times to the champion. The number of players wearing scarlet and blue that had never represented anybody else: eight.

"It looks easy, but it isn't," Messi told the press after the match. Barca's flowing play is the result of its players having competed together for 10 or more years. It's also evidence that in the sporting and social sphere, the value of the one-club player cannot be understated.