Lukasz Fabianski has been an absolute revelation since arriving at West Ham from Swansea last summer.
Tipped by yours truly to be the standout signing of the 2018/19 season, the Pole lived up to expectations by immediately ousting Adrian from the starting lineup - completing all 38 Premier League games as he helped secure a top-ten finish.
In the process, he became one of the most important names on Manuel Pellegrini's team sheet - winning the prestigious Hammer of the Year award as he swiftly became a fan favourite.
So the news that he'll most likely be sidelined until the new year is a crushing, crushing blow for the Hammers.
Outside of an opening day mauling at the hands of free-scoring Manchester City, as well as an instantly forgettable Carabao Cup humiliation to Oxford, it's been a really good start to the 2019/20 season for West Ham.
Unbeaten in six, the Hammers are punching above their weight in fourth place - having bedded in new signing Sebastien Haller nicely, as well as welcoming back Andriy Yarmolenko and Manuel Lanzini from long-term injuries.
Such is the impact those three have made, they've stolen the headlines on the whole - along with a rejuvenated Aaron Cresswell and the ever consistent duo of Mark Noble and Declan Rice.
But deep down, all West Ham fans know that the confidence and belief of the team stems from the knowledge that they have a top class keeper in goal. Safe in the knowledge that they have Lukasz Fabianski between the sticks.
So, when he went down midway through the first half of the weekend clash against Bournemouth, every West Ham supporter at the Vitality Stadium took a deep breath. Hoping, praying and anxiously watching on as he was attended to by the club's physios.
The news unfortunately is not good. Fabianski is staring down the barrel of missing three months of action with a torn hip muscle, ruling him out until 2020. It's not only a bitter blow for Fabianski himself, but it's a huge concern for Manuel Pellegrini and the club.
His form has been nothing short of sensational since arriving in east London, evidenced by his winning of the club's best player award. 148 saves saw him complete the most saves in the Premier League last season, seven more than any other goalkeeper, at a remarkably high 73% save percentage.
On occasions, he made truly incredible saves - ones against Callum Wilson and Marouane Fellaini at the London Stadium spring to mind - and single handedly has earned West Ham points they wouldn't have picked up in his absence.
But it's his calming presence that will be missed most. Just knowing that he's not in goal will pose problems to West Ham's defence, regardless of how good Roberto might be as he steps into the breach.
Defensive fragility and mental meltdown have long been associated with the Hammers, with the occasional collapse marring generally good progress - particularly under Pellegrini. Barring some cup disasters, neither of which Fabianski has played in, you feel that West Ham's mindset has changed with the former Swansea stopper in goal.
That could all change now.
The hope is that Fabianski recovers quickly, and hits the ground running when he returns. Confidence plays a big part in goalkeeping, and he's had plenty of it over the past five seasons - only missing three games out of a possible 190 since leaving Arsenal in 2014.
You also hope, from a West Ham point of view, that Roberto can cope with the pressure of regular football. He may be 33, yes, but he's not overly experienced as a first-choice keeper in top-flight football and has memories of that 4-0 Carabao Cup drubbing at Oxford fresh in his mind.
If only Adrian had been convinced to sign a new deal, eh?