It was only eight years ago that a fresh faced Marko Arnautovic was sharing a dressing room with the likes of Javier Zanetti and Samuel Eto'o, and with it being labelled as 'childlike' by his then-Inter manager Jose Mourinho.
Fast forward to today, and whilst Mourinho struggles to get to grips with the increasing pressures at Old Trafford, the Portuguese coach may just call on a boy turned man to solve his non-stop problems in Manchester. Step forward Arnautovic.
Back then, Arnautovic's immaturity, mixed with his arrogance, didn't bode well in a team full of star players, who were on the cusp of greatness.
During Mourinho and Arnautovic's time at the San Siro, the number three ended up signifying a historical and forgettable time for both men at the Italian club.
For the now Manchester United manager, it echoes fond memories of a treble-winning side, including lifting the Champions League. For West Ham's talisman, it only reminds him of the number of games he ended playing for the club during the most successful period in their history.
Not many would argue that in 2010, the then 21-year-old Arnautovic, didn't have the mindset to play at the highest level, despite the Austrian possessing a Zlatan Ibrahimovic-like physique and a natural talent that any other young footballer would dream of possessing.
Not forgetting, he was sharing a training ground and dressing room with some of the great coaches and players in the game. But still, it wouldn't click for the Austrian international.
With age comes maturity, and with age comes wisdom. And there is no doubt that Arnautovic falls into both categories as he is now rightly being tipped for a move back to the big time.
Over the last 18 months, the powerful forward has taken his game to levels above those around him as he constantly showcases, week in and week out at the London Stadium, that he is now ready to fulfil his true potential.
Since his £25m move from Stoke to West Ham, Arnautovic has scored 16 goals and provided nine assists for a team that has, for the majority, struggled to perform on a consistent basis in England's top flight.
Whilst Manchester United fall increasingly behind their neighbours, Mourinho needs an injection of life in January that could reinvigorate his fledgling offence.
That once-childlike player could be the man to save Mourinho from falling even further, and his former coach could help him reach the heights he should have been aiming for all those years ago.