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Midway through September, Spain met Montenegro in a UEFA European Under-21 Championship qualifier in CD Castellon's stadium on the east coast of Spain.

The game was only three minutes old when Spain's Marc Cucurella crossed to Dani Olmo. From outside the area, Olmo controlled the ball with one touch and then blasted it into the top corner. A few minutes later, Olmo intercepted a loose back pass in Montenegro's box and nutmegged their goalkeeper.

He had scored two goals with less than 10 minutes played in the match. Job done. Spain won 2-0.

After winning their fifth under-21 European football title this summer—Olmo scored three goals in the tournament, including one in the 2-1 final win over Germany—it looks as if Spain are already contenders to retain their crown. Olmo, the team's captain and No. 10, is leading the charge.

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He was a forgotten young man, but his name is now on everyone's lips in Spain.

"Almost nobody knew about his existence—except for the most specialised football followers—until the European Under-21 Championship this summer, when people saw him playing and helping Spain to win the tournament," says Juan Bautista, a journalist with Barcelona-based newspaper La Vanguardia. "That was when people discovered there is a boy called Olmo that one day used to play in Barca."

Olmo has taken the road less travelled. His under-age career started brightly when he joined Barcelona's youth academy from Espanyol in 2007. He was nine years old. He became part of a talented generation that included first-team players Carles Alena and Carles Perez, Cucurella (who is on loan at Getafe) and Barcelona B's tenacious full-back Dani Morer.

"He was very good that season with me," says Denis Silva Puig, who trained Olmo at La Masia during the 2010-11 season. "He was a typical forward, a very good finisher. He scored goals in every age category, and, of course, as a forward, it's the first thing you notice about him—he has always scored a lot of goals. He understood space well, so he could find room to score. He's a natural-born goalscorer."

Olmo finished as the top scorer in four of his six seasons at La Masia. He then left before signing his first professional contract. He had several offers on the table from English Premier League clubs in the summer of 2014, but he decided to head east to join Dinamo Zagreb.

That he left Barcelona came as a surprise. He'd dropped down the pecking order at La Masia.

"He left because two Korean players arrived—Kyeol-heui Jang and Lee Seung-woo, a winger and centre forward," says Silva Puig. "They were two cracks [star players]. Let's just say that final year, he was a little bit marginalised on the under-16 team. He didn't play much. Lee and Jang played more. They [muscled] him out. They had big reputations, a media presence behind them. It was unsettling for him. For this reason, I believe he decided to leave.

"It was bad news for Barca that he left. He had a great future ahead of him. For sure, Barca regret losing him. He could have stayed and made it onto Barcelona B. But of course, we couldn't know what way he would turn out. It's always difficult to know. With a talented player, it's easy and fast to recognise his talent. He's got the same talent at 10 years of age as he has at 18 years of age. A different thing is knowing the career they could have. How far they can go."

Olmo's case was rare.

Every year, gifted players leave La Masia. For example, go back to when Arsenal lured Cesc Fabregas away in 2003. Within a few weeks, Arsene Wenger had parachuted him into the first team at 16 years of age.

In 2017, Manchester City enticed defender Eric Garcia to try his luck in England. Pep Guardiola gave him his English Premier League debut earlier in September against Watford. He's still only 18 years old.

During the summer, Paris Saint-Germain plucked 16-year-old Xavi Simons from La Masia, reportedly giving him a contract worth €1 million per season, according to Mundo Deportivo's Angel Perez.

What was different about Olmo's case was that he went to Croatia, one of Europe's less glamorous leagues.

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"It was a special case, going to a type of club like Dinamo Zagreb in Croatia," says Silva Puig. "We hadn't seen a move like it before. It wasn't like the case of, say, Eric Garcia when he got an offer for a lot of money from Manchester City. Dani took a risk—a kid of only 16, moving to another culture.

"It's always a risk, but when things go well, you can always say you were right. I think it's never wrong to leave Barca. I always tell this to the boys when they have offers like, for example, Ansu Fati. He had an offer [earlier this year], and I talked with him and told him, 'I can't tell you if Barca is the best place to be. It's a lottery,' [but] when you leave, you never know. In the end, Dani left, and he has being doing well. I'm very happy for him."

Olmo's decision to strike out in one of Europe's more far-flung leagues suggested he was a young man who knew his own mind.

"It shows he's a player with a recognisable mental strength," says Bautista.

Olmo has always been a leader. He's captained many of the teams he's played on—when he was at La Masia and with Spain's under-age teams. He learned about the game at the feet of his father, Miquel, who is a former professional footballer in Catalonia's lower leagues.

"Dani is a serious guy," says Silva Puig. "He's a very hard worker. He never caused problems. He's very professional. He's got a very Barcelona-type profile. He knows football. He comes from a football family—his father was a player and is a coach. He has a lot of influence on Dani.

"I coach lots of players from normal [non-football background] families. It's totally different when you have a kid who comes from a footballing family. If a player's father was a professional footballer, he guides his son. Dani's brother plays football as well. Since Dani was young, he was very clear about his future—it's a widely known aspect about him. And if he had to jump to a place like Croatia to secure his future, because he sees that could help him later on, he would do it."

Olmo has prospered in Croatia. He was fast-tracked into Dinamo Zagreb's first-team squad, making his debut in February 2015 at the age of 16, and he has been scoring at will since. He was named Croatia's Player of the Season last June, and he ran Atalanta ragged in his UEFA Champions League debut in which a Dinamo Zagreb side cobbled together for €6 million defeated the Serie A side 4-0.

"A lot of Dinamo Zagreb's fans hadn't heard of Dani Olmo up until his debut in the first team," says Juraj Vrdoljak, a journalist with Croatian website Telesport. "He was in the reserves, but people within the club quickly realised that he was mature as a player and he had to be given a chance in the first team.

"He was still very young. Fans were saying, 'Hey, perhaps he isn't much of a talent if Barcelona gave him away so easily, if he decided to go to the Croatian league,' regardless of the fact that Dinamo has a history of selling young players for lucrative fees. But once he started to make his mark in the first team, people wondered how come a talent like this made it from Barcelona to Croatia.

"He's become the team's best player, and maybe even the best player in the modern era at Dinamo. People compare him to Luka Modric, who started off as an attacking midfielder. You can draw similarities between them—as the next great player who is even outdoing Modric's time at Dinamo."

Olmo is at a crossroads. He might have hit a ceiling at Dinamo. The Croatian club slapped a €40 million price tag on him after his UEFA European Championship Under-21 heroics in the summer. His contract runs until 2021. Only Bundesliga side Borussia Monchengladbach—who tabled an offer of €20 million—came in with a formal bid, which was rejected. A romantic return to Barcelona—which Mundo Deportivo hinted at—seems unlikely.

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"I sincerely haven't heard anything about him [returning to Barcelona] inside the club. It would be difficult, very difficult, but, hey, you never know," says Silva Puig. "Other young players have recently arrived onto the first-team squad—Carles Perez, Ansu. There has been talks of Neymar returning.

"There are cases like Gerard Pique, who returned [from Manchester United], but it would be complicated. I'm surprised he hasn't returned to Spain at this stage, for example, to a mid-table team in the premier division, like Villarreal, Valencia or Celta Vigo. His club might be looking for too high a price."

All eyes will be on his performances in the Champions League, in which he will line up against Guardiola's Manchester City on Tuesday at the Etihad Stadium. Dinamo Zagreb's return to the competition for the first time in three years has put him in football's greatest shop window. It appears as though he's being fattened up for a heftier sale in the January market.

"What's really comforting—if Olmo manages to get his breakthrough at the top level with a club in Europe's top five leagues—is that he will be a great example for different young players from western Europe," says Vrdoljak. "Because no one really expected his career trajectory to go this way—going from Barcelona to Dinamo Zagreb, which in wider terms is a relatively obscure team. If you asked people on the streets of Barcelona where Dinamo Zagreb is, the chances are that most people wouldn't know.

"Olmo serves as an example for some kids who don't get a chance in big clubs that in central and eastern Europe, there are clubs who are willing to give players a chance. Even if it sounds weird at first, the biggest risk is to sit around wasting your formative years. In his search for playing time, it's a gamble that is paying off for Olmo."

Follow Richard on Twitter: @Richard_Fitz