Kepa Arrizabalaga is under scrutiny as his poor statistics become public knowledge but Chelsea have long been aware of their No. 1's shortcomings.
Of the 116 goalkeepers to have played at least five games in any of Europe's 'Big Five' leagues this season, the £71 million signing from Athletic Club ranks 109th in terms of save percentage, while he also has the fewest 'expected goals' [xG] prevented in the Premier League.
Kepa was criticised in some quarters for conceding twice from the two shots he faced in Tuesday's 2-2 draw with 10-man Arsenal but it would be harsh to blame him for either goal.
Nonetheless, his kicking was wayward throughout and repeatedly put his own team under pressure during another unconvincing display.
Consequently, Chelsea intend to look at other goalkeeping options during the summer if Kepa can't arrest his worrying dip in form.
Frank Lampard stopped short of admitting that Kepa's position is under threat but he did concede he wasn't entirely happy with the Spain international's distribution against Arsenal.
"I know there's a focus on him at the minute. That's top-line football," the Blues manager said.
"Yes, with his feet, a couple of times today he took too long and he nearly gave it away. That can sometimes change the momentum of a game. He knows that himself and he has to look at that. And we have to look at that too..."
Lampard elaborated on the theme on Friday. “I am not looking at strengthening that position now but Kepa knows that there have been some mistakes and is honest about that," he said.
'Now' was very much the operative word in that sentence. Chelsea certainly didn't envisage having to even contemplate looking for a new No. 1 when they made Kepa the most expensive goalkeeper in the world in the summer of 2018.
The 25-year-old was considered one of the top shot-stoppers in La Liga when he was signed to replace Thibaut Courtois.
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However, it is worth remembering that the Blues only made their move after numerous failed attempts to sign Alisson from Roma, with the Brazil international preferring to join Liverpool instead.
It was known within the football community that Kepa's good distribution wasn't matched by his reflexes and agility in between the posts. However, it was thought that he could and indeed would improve with the ball at his feet.
It is deeply concerning for Chelsea, then, that he doesn't appear to be getting any better. If anything, he has gone backwards under Lampard after a reasonably good first season at Stamford Bridge under Maurizio Sarri.
Indeed, his percentage of shots saved has dropped from a middling 67.8 last term to a lousy 55.56. He is also producing more inaccurate passes for his new manager, with his 85.4% pass completion rate in the Premier League dropping to just 78.38%.
Mistakes against Arsenal and Man City went unpunished but he sealed his side's fate in the 3-1 loss at Everton when he gave the ball away to gift the home side the killer third goal in the closing stages.
The data shows that Kepa has conceded 6.62 more goals in the league than Opta stats would have predicted and these metrics are something that Lampard takes seriously.
Indeed, Lampard is on record admitting that he is disappointed with the fact that Chelsea are not performing poorly in terms of expected goals at the other end of the pitch.
"I don’t like too many stats on expected goals because it is not all that clear at times, but we are bottom of the league in terms of our numbers at home," he pointed out, "and we’re probably second only to Liverpool.”
Lampard has been quick to defend Kepa, pointing to big saves in the recent draw at Brighton in a bid to boost his goalkeeper's confidence.
However, even aside from the statistical evidence, Kepa has noticeably struggled with long-range shots and close-range headers, with Chelsea conceding worryingly similar goals against Newcastle, Ajax, Arsenal and Wolves this season.
There have been reports that Lampard would like to bring in former Republic of Ireland international Shay Given, who was in his backroom team at Derby County, but the manager has denied that he is looking to get rid of his current goalkeeping coach, Henrique Hilario.
Perhaps the best thing for Kepa right now would just be some time out of the limelight, which makes the timing of this weekend's FA Cup clash with Hull City particularly opportune, with Willy Caballero set to start anyway.
Of course, Caballero will be sensing an opportunity himself, having rarely featured this season apart from in the domestic cup competitions.
This is his chance to shine while some supporters are calling for him to start in the Premier League.
The situation is clearly a delicate one and Lampard will need to manage it carefully, particularly as he will not want to dent Kepa's confidence.
However, while Chelsea stood by Kepa after his moment of madness in the Carabao Cup final last season, Lampard might be less forgiving than Sarri given the goalkeeper's performances are so obviously in decline.