Such is the intensity of competition for the allegiance of the Scotland-born but Australia-raised midfielder, that Australia coach Graham Arnold took the unprecedented step of inviting him to join his Turkey-based camp for Socceroos present - and future - earlier this month.
Football Federation Australia received a letter back from City claiming that Robertson - whose father Mark and grandfather Alex both played for the green and gold - was injured.
He was also offered the chance to represent Australia at the AFC Under-16 Championship, which kicks off on Thursday in Kuala Lumpur.
Again, the FFA drew a blank with fears mounting that his courtship with England - for whom he claimed his first two caps in August at Under-16 level - could lead to a committed relationship.
The Three Lions coach Kevin Betsy has been assiduously wooing Robertson, who scored the winner against Turkey in last month’s UEFA Development Tournament.
But Luke Casserly, FFA’s head of national performance and a former teammate of Mark Robertson at national team and club level, is fighting to turn his gaze back to Australia.
“We’ve been constant contact with his father (Mark) and he was invited into the camp in Turkey and also to Malaysia with the Joeys,” Casserly said.
“He’s an exceptional prospect and we’re doing all we can to get him to commit with us in the future.
“The idea of him coming to Turkey was to show him, were he to choose to play for Australia, what that pathway would involve and where he could end up.
“We got a letter from City saying he was injured but there was no medical report or explanation of the injury.
“Reading between the lines I feel the family are a bit reluctant to commit right now to any nation in particular.”
Robertson is also eligible to play for Scotland and Peru, courtesy of his mother.
He can be capped at youth level for any of the four countries, his allegiance only becoming binding when he represents one of them at senior level in an official match.
“I feel they’re (his family and advisers) cooling their heels a bit right now and deciding on what’s the right path,” Casserly said.
“We’ve gone to great lengths already to show him highly we regard him - but ultimately the decision is down to him.”
Robertson was blooded by NPL club Hakoah, formerly coached by his father, but left with the family for the UK over three years ago.
So eye-catching was his talent that he joined Manchester United’s youth ranks only for eternal enemies City to snatch him from under their noses 11 months back, after the Red Devils dallied over a formal contract offer.
Family friend and leading Australian player agent Ante Alilovic believes Robertson has been allowed to slip through the system and is “feeling more love from England than Australia”.
“He’s been flying at City, scoring goals and getting man of the matches,” Alilovic said.
“The England junior ranks are very powerful now. They’ve won the Under-20s and 17s, and in Alex they’ve got a box-to-box player who was really overlooked here because coaches are scared to take the risk.
“Previously, he only wanted to play for Australia now it’s not so cut and dried.
“England are constantly in touch, offering him help with anything and everything and are showing him the love.
“I don’t think he’s getting anything like that from Australia.
“He says his heart is a bit torn but Australia is still his pride and joy and he wants to play for them.”
But Casserly disputes that Robertson has been allowed to drift away from the national team, insisting his current ties to England could be as much to do with logistics as anything else.
“Trevor Morgan, the Joeys head coach, has had a number of conversations with Alex directly and I’ve spoken a lot with his father, who I consider a mate,” Casserly said.
“We’re not there on the spot and it’s easier for England, and maybe more suitable for Manchester City, for him to be going into camps at St George’s Park rather than flying to the other side of the world.
“Unfortunately for us, a player like that could make a big difference in qualifying for a World Cup. But we’ll keep plugging away at this.
“I’ve been watching Alex play since he was eight. He went to Westfield’s Sports High, and we know everything about him and we’re very keen to have him play for Australia.
“Hopefully in time, when it becomes crucial for senior football, he’ll choose Australia.”
It’s understood that no less than Michael Owen, the former England, Liverpool and Manchester United striker turned player agent, currently represents the youngster.
Alex first came to Australia aged five after dad Mark’s professional career in the UK - at clubs like Swindon, Dundee, St Johnstone and Stockport - wound down.
“He’s certainly not one who’s slipped through the cracks,” Casserly said.
“He’s a very confident boy who sees and understands the game very well.
“He’s very mature for his age and has an excellent understanding of the game.
“He’s a midfielder who has that ability to score goals as well. He also has an excellent passing range and is a very talented prospect.
“He looks good but he is still very young and there’s a long way to go.”
The hope is he will make the journey with Australia.
