His performance against Liverpool in the Champions League in particular was one of the all-time great performances in any competition, and went some way to helping the Parisiens get to the final and win the trophy for the first time in their history.
No sooner have the club finished their - ultimately unsuccessful - attempt at winning the Club World Cup than Luis Enrique dropped the bombshell.
"Donnarumma is one of the best goalkeepers in the world, without a doubt, and even better as a person," he said in his pre-match press conference for the UEFA Super Cup.
"However, this is the life of a top-level footballer, and I am 100% responsible for this difficult decision. If it were easy, anyone would do it. These decisions have to do with the profile of the goalkeeper my team needs."
Since 2020/21, Donnarumma has played in 151 games for AC Milan and PSG and started in them all, however, there's long been question marks over the Italian's footwork.
Is perception clouding the reality for Donnarumma?
What's interesting is if you look into the details, his 51 successful keeper sweepings from 53 attempted gives him a lowest stat of 90%.
His passing more generally, in league games only during 2024/25, was at a healthy 85.4% too, only just shy of the previous campaign's 87.1% and better than 2022/23's 84%.
That accuracy goes up to a sensational 94.7% when looking solely at passes in his own half. Pretty incredible, right? Could perception, therefore, be clouding the reality?
Though it's true that he does find it difficult to get down to low shots, he is a huge 6ft 5in tall and given that he's saved his team more often than not, his height shouldn't be used as a stick to beat him with.
A save percentage of just 66.2% in the 24/25 Ligue 1 campaign was his worst at the club and a big drop off from the previous season's 81.8%, and longer passes of 30 metres or more have almost certainly contributed to Donnarumma's downfall.
That's because just 16 were completed from 69 attempted in Ligue 1 last season and 60 overall completions from 284 attempted is a roughly one-in-five success rate. That isn't really good enough at the top level.
Contract uncertainty
Given the uncertainty surrounding whether he was going to sign a new contract or not too - it's rumoured he wanted a 50% uplift on his €244,808 (£213,292) weekly salary - it's not beyond the realms of possibility that a decision was also taken with that in mind.
It's clear that the decision deeply disappointed the keeper who took to social media to say his goodbye.
Earlier in the summer, it was thought that Manchester United were considering taking the keeper to replace their error-prone stopper, Andre Onana. However, their dilly-dallying and subsequent purchases, including Benjamin Sesko, appears to have hamstrung the club in trying to construct an acceptable deal.
Despite recently signing James Trafford from Burnley, it's understood that Manchester City have agreed terms with Donnarumma, but any transfer is dependent on Ederson moving on.
Donnarumma move dependent on departure
The Brazilian is also in the final year of his contract, and it's understood that he is more than willing to run it down in order to make a more lucrative switch in a year's time.
However, Galatasaray are circling for the soon-to-be 32-year-old, and it may be that Pep Guardiola feels that the time is right to ease Ederson out of the Etihad Stadium exit door.
His save percentage of 67.1% from last season's Premier League is only slightly above Donnarumma's, though an 84.6% success from those outside of the box was far in excess of the Italian's 73.9%.
Both custodians have 13 catches and 16 dropped balls over the past four seasons, with Donnarumma's 43 punched clearances four more than the Brazilian.
The Italian surprisingly has only saved three of the 16 penalties he's faced in domestic competitions since 2020/21, though Ederson's one from 18 is nothing to write home about either.
Will Ederson dig his heels in?
22 accurate sweeper keepings last season from 23 attempted gave the latter an impressive 95.7% accuracy, and whilst still not as good as Donnarumma's 100% accuracy, it must be factored in that he only had eight to contend with.
Perhaps Pep Guardiola sees something in the younger man that he can work with and develop, but if Ederson digs his heels in, there's a very real prospect of City missing out.
For a player of such evident capabilities, to then see the 26-year-old having to hunt around for a new club in the final days of the window just doesn't seem right.
