Just as AC Milan appeared to be in the process of assembling a squad that looked capable of lifting the club back to the top of Italian football, their hugely talented young goalkeeper Gianluigi Donnarumma threw a spanner in the works.

The 18-year-old informed the Rossoneri on Wednesday that he will not be renewing his contract at the San Siro.

Donnarumma’s current deal expires next summer, meaning Milan will lose him for free in 12 months time unless they cash in now or in January.

Real Madrid and Paris Saint-Germain are understood to be at the front of the queue and a transfer to one of those clubs could now be finalised ahead of the 2017-18 season.

It’s undoubtedly a huge blow for Milan, who are poised to lose the services of the best young keeper on the planet. Replacing him won’t be easy.

Milan fans assumed Donnarumma would renew his contract due to the fact he supported the club and appeared to be happy at the San Siro. He was playing week-in, week-out, so why wouldn’t he be?

What Donnarumma said about Milan in 2016

It was the Rossoneri who gave the teenager his big opportunity aged 16, putting a huge amount of faith in a goalkeeper so young, and just last summer he told reporters that his dream was to captain the club.

"I really like the idea of renewing my contract and I also like to think I will have a lasting relationship with Milan for the coming years," he told the La Gazzetta dello Sport, per Goal, in July 2016. "I've always been a Milan supporter and I must say the captain's armband is a dream of mine, a crowning achievement in my career path.”

What’s happened since then, Gianluigi?

The man who discovered Donnarumma isn't surprised

Although Donnarumma’s decision has stunned Milan fans, one person who isn’t surprised is the scout who discovered the keeper in Naples, Giocondo Martorelli, who insists the warning signs have always been there.

“I might come off as unpleasant to some, but I was one of the very few people who saw this coming,” he told TMW Radio, per the Mirror, on Thursday. “Knowing various situations, at Milan before and also after, it’s not surprising that Donnarumma won’t renew the contract. It’s a problem that needs to be tracked down to the start to understand who is responsible for reaching this point, a year before the end of the contract.

“I know everything about Donnarumma – his family, relatives, every corner of his home. There are things that really surprise me, namely that big newspapers and television stations pretended not to know what was behind him and always has been. Donnarumma’s history is complex and this is the final result of behaviour that hasn’t been fair from the start.

“I wouldn’t say I discovered him, as I was just fortunate to be in the right place at the right time. He was 10 years old and even a blind man would’ve been able to tell Donnarumma was a talent.

“I saw this kid in Naples and immediately called Piero Ausilio at Inter. For three-and-a-half years, up until 2013, he was being groomed by Inter and had several trial runs there.

“It all went fine until the moment he was set to sign the written contract with the club. That afternoon, we all reached an agreement – him, his father and mother – after four intense years.

“The next morning, they agreed terms with Milan, without warning or fair play. There were some precedents that made me think Donnarumma could get into this situation with Milan.

“I am perplexed at his decision not to stay with a club like Milan, but then I have my ideas on the matter.

“I’ll just repeat: his family in 2013 signed for Inter. They returned to Naples, the next morning took a plane and signed for Milan. The contract they had signed less than 24 hours earlier was worthless.

“What more do I have to say? I am stunned that some reporters continue to not know the situation or pretend not to listen.”

Can Milan recover from this setback?

Milan must now ensure this major setback doesn’t ruin their plan of recovering after several seasons in the doldrums.