Dortmund could have bargain in former Man City youth star Jaden Sancho

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Pep Guardiola has spoken excitedly about the youth prospects coming through Manchester City's Academy, and said before the summer that he was looking to give them an opportunity to impress on the club's preseason tour to the United States.

It was generally thought he was referring to City's highly-rated trio: Stockport-born midfielder Phil Foden, Spanish forward Brahim Diaz and skilful winger Jadon Sancho. Foden and Brahim both took their chance brilliantly with impressive performances and will spend the season with the first team, hoping to push Guardiola into giving them some minutes on the pitch.

Sancho, however, was surprisingly left behind. Barely a month after the squad reconvened in Manchester, he was headed out to Borussia Dortmund in an £8 million deal. In the short term it's a good deal for City, particularly as they were reportedly only due £170,000 through FIFA rules and the fee could rise to £10m with add-ons -- City have also included a "substantial" sell-on clause. But there will be frustration that a player with huge potential won't be making the grade at the Etihad Stadium.

City are desperate to start producing their own first-team talent from their £200m state-of-the-art academy campus and chairman Khaldoon Al-Mubarak had name-checked the 17-year-old Sancho in his end-of-season statement to fans as one to look out for.

"You look at Sancho, you look at Phil Foden, you look at Brahim Diaz, just to name a few. These are players that are extremely talented. These are players who have a very good chance of making it to the first team," he said. "And these are players that if you ask Pep today, he will tell you they can and will be first-team players at Manchester City."

There is no doubting Sancho's talent. He was named the Golden Player at the European Under-17 Championship in May, when he scored five and assisted five of England's 15 goals in their run to the final. Sancho and Foden's performances were noted by German coach Christian Wuck, who was effusive in his praise. "Sancho and Foden are very good. I've never seen better players than these two at this age," he said.

Sancho, who joined City from Watford in a £500,000 move in 2014, had already become a key player of City's youth team. They dominated other sides on their way to the FA Youth Cup final, where they were beaten by old adversaries Chelsea for the third successive year. And in one game in last season's UEFA Youth League away to Barcelona, he tormented the home defence to such an extent that three of the shattered back-four sunk to the floor at full-time despite winning the game 1-0.

Sancho was still a scholar and had turned down a professional contract amid interest from Dortmund and fellow German club Red Bull Leipzig. English clubs Arsenal, Tottenham Hotspur and Manchester United were all linked with him. Sources have told ESPN FC that he had failed to turn up for a number of training sessions with City after the tour, and the Daily Telegraph reported that club officials had been unable to get in contact with him.

City had hoped to resolve the situation but Sancho decided his future lay elsewhere and moved to Dortmund, where they have given him Ousmane Dembele's old No. 7 shirt.

"It was a difficult decision, but the time is right for a new challenge where I can start to fulfil my potential," he said in a farewell message on Twitter, which also thanked the club and staff for helping in his development.

Dortmund's investment in him is sizeable but it could be a bargain if he goes onto replicate the form of predecessor Dembele, who has just completed a £97m move to Barcelona at just 20 years old.

The size of the fee and giving him the No. 7 shirt would suggest that Dortmund believe he's ready. At City, his squad number was 48 and unlike Foden and Diaz, he has never been a part of the match-day squad. But it could also place a lot of pressure on a player at a club that will believe they should be competing for the Bundesliga title.

For all Sancho's undoubted skill and ability, there were reasons why he wasn't considered ready for the first team -- most prominently his decision-making, which should improve with experience. Guardiola also watched City's FA Youth Cup first leg against Chelsea, when Sancho struggled to make an impact against a club that has dominated youth team football in recent years.

But Sancho's raw talent is unquestionable, and Dortmund's belief in him and track record for bringing through their own players makes this deal one of the most fascinating of the transfer window.