Editor's note: Tor-Kristian Karlsen is a Norwegian football scout and executive, formerly the chief executive and sporting director at AS Monaco. In his latest column on the business of soccer, he looks at some of the players who were unable to live up to the impression they made when bursting onto the scene.

Sometimes a scout's job is easy. You spot a player so outrageously talented, so far above his peers that there seems no question or risk; it's just whether you can get there first to sign him. The teenage Neymar and Sergio Aguero are examples from my own old notebooks of those about whom I sent 'must-have' reports, along with the rest of the world! But while scouts and sporting directors are happy to share success stories, sometimes we get it wrong. There are names who were predicted to have glittering careers, only to never fulfill their potential.

Those of us watching 16-year old Colombian Johnnier Montano at the 1999 Toulon Tournament -- the top showcase tournament for Under-20 players at the time -- could be forgiven for thinking they had seen the next big thing. Juan Roman Riquelme had starred for Argentina in the 1998 event and we were keen to see if there would be anyone of his quality the next year.

What Montano served up was nothing short of spectacular. From his No. 10 role, he would launch long-distance shots by way of a wonderful left foot, playfully slalom past opponents with great ease, ping pinpoint passes behind the opposing defence and execute triangles and one-twos with teammates. There was pretty much everything you wanted from an attacking midfielder, right there in front of your eyes, courtesy of an unknown Colombian teenager.

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The turn of the century was approximately a decade before video scouting -- let alone streaming services such as Wyscout or InStatScout -- became omnipresent, so reliable information was scarce. Such was the buzz around Montano that there was a rush to be first on the phone to sporting directors or managers. To the disappointment of many, however, it emerged that Montano had committed himself to Parma.

The-then affluent Italian giants must have thought they had landed another Faustino Asprilla, another Colombian who starred in Italy, and who could blame them? Montano looked like a star in the making and that same year -- with the Toulon Tournament Trophy and MVP award in the bag -- starred for his country at the Copa America, where he became the youngest scorer in tournament history with a goal in Colombia's 3-0 hammering of Argentina.

But he did not settle in Italy, making just one start for Parma plus a couple of dozen appearances on loan at Verona and Piacenza. After then spending his early 20s back home in Colombia, Montano moved to Peru where, with the exception of short cameos in Qatar and Turkey, he spent the rest of his career, becoming a cult hero at clubs like Alianza Lima, USMP and Sport Boys.

Another talent on display in France all those years ago was Daniel Montenegro. Four years older than Montano, the Argentinean playmaker's game was more structured and mature, but there was a general consensus that his "peak" would be Champions League-level, whereas there were no limits for Montano.

Montenegro earned himself a short stay with Marseille as a result of standing out at Toulon, though his career highlights were played out in front of crowds in his homeland or with Club America in Mexico. His fellow countryman Andres D'Alessandro had a similar story: Star as a youngster at home, struggle to live up to promise in Europe, return to South America and achieve success (D'Alessandro is a legend at Internacional of Brazil).

In 2011, European scouts gathered in the southern Peruvian city of Arequipa for the South American U20 Championship. Although the tournament is best remembered for an amazing Brazil side that comprised the likes of Neymar, Lucas Moura, Casemiro, Alex Sandro and Danilo, most exciting was the emergence of 17-year-old Juan Iturbe, winger/second striker about whom there had been plenty of talk after he broke into the first team of top Paraguayan club Cerro Porteno.

At first glance, the stocky, explosive Iturbe appeared to have the intensity on the ball of Carlos Tevez and the and the explosivity and one vs. one skills of Lionel Messi. Though he excelled and frustrated in equal measure, Iturbe possessed the raw "street footballer" edge that is almost unique to Argentinean forwards. There was hardly a scout in Arequipa, who was not prepared to take a punt on him, but, not for the first time, Porto were one step ahead and rushed in to secure a deal with the player's agents and family while the tournament was taking place.

Nine years later, and still only 26, Iturbe is trying to find his feet in Mexico. He spent a successful 2014-2015 season at Verona, which led to a €20m move to Roma, but since then his career has consisted of failed loan moves including one in the Premier League for Bournemouth that entailed just four appearances in all competitions.

The list goes on; many will remember Florent Sinama Pongolle securing a move to Liverpool on the back of a remarkable nine-goal scoring spree at the 2001 Under-17 World Championship, while Souleymane Coulibaly earned a contract with Tottenham after reaching the same tally at the same competition a decade years later. Both were predicted to have great futures, but neither managed to consistently perform.

Among plenty of examples from recent years, Lazar Markovic is probably the most extreme example of the discrepancy between intrinsic ability and actual end product. The Serbian winger, who joined Liverpool from Benfica for €25m in the summer of 2014, has only just turned 26 and so still has time on his side, but how he could go from such a most coveted young star -- tipped to star in Europe's top leagues -- to having to kick-start his career at hometown club Partizan Belgrade is a mystery.

The integration of data and analytics, as well as an array of footage, better sources and a wider range of information have certainly helped clubs mitigate the risk element to transfers. For the player, though, choosing the environment and head coach that best suit your needs -- on and off the pitch -- remain critical aspects when forging a career path.

As for the scouts, whose job it is to first identify ability, the search for the next hot prospect continues. Indeed, those reading might like to note that Johnnier Montano Jr. has just been selected for Colombia's Under-16 team...