Timo Werner, Kai Havertz, Hakim Ziyech, Thiago Silva, Ben Chilwell - none of Chelsea's summer signings can claim to have had such a dramatic effect on the Blues' fortunes so far this season than Edouard Mendy.
Mendy, acquired for £22 million ($29m) as the final piece of Frank Lampard’s summer transfer spree, is now set for a rapid reunion with former club Rennes as Chelsea prepare for their Champions League showdown on Wednesday.
The goalkeeper goes into the game having not conceded a goal in his last 457 minutes on the pitch, and with five clean sheets to his name from six appearances in a Chelsea shirt.
Given the west London outfit shipped 54 Premier League goals last season, few saw their transformation with a new man between the posts coming quite this quickly.
While Chelsea may still be conceding an average of two goals per game when Kepa Arrizabalaga is playing, that figure reduces to only 0.25 goals per game when Mendy is selected.
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But the Senegal international has not just made an impact with his shot-stopping capabilities; he is also collecting crosses with authority and dealing with one-on-ones with more confidence than the world's most-expensive keeper.
Mendy's ability is underpinned by not just his size - at 6’6" - but also his speed.
That was highlighted both by his quick reactions to Kurt Zouma missing an early cross against Burnley on Saturday as well as his adeptness at closing down Ashley Barnes, who was through on goal.
“He has been great with the ball at his feet and he is big too,” said Zouma after the 3-0 win on Saturday. “He has presence and catches the ball when he comes out. He is talking a lot, doing a great job. He settled in very quickly, but we have to keep focused.”
It is hard to quantify just how pivotal these moments have been; it could be that they have impacted results as much as goals at the other end, such as Hakim Ziyech’s opener in their last Premier League outing.
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Overall, Mendy's presence has lifted the performance levels of the defenders in front of him.
They now look more assured as each game goes by with their confidence in their goalkeeper growing all the time.
That is in significant contrast to last season, when Chelsea's defenders were understood to have lost confidence in Kepa, particularly relating to his shot-stopping and ability to claim crosses.
"I tried to support Kepa and Willy [Caballero] as much as I could in training, which was what I did," the Stevenage loanee said in an interview with Goal last week.
"Kepa is a top keeper, I am sure he will get out of the run he is in, things go wrong, the media slam you and it is not easy. I am still sure he is mentally strong enough and he definitely has the ability."
The £72m ($80m) club-record signing registered the worst save percentage in the Premier League last season at 53.47 per cent, which only increased slightly this season to 57.14% before his dropping.
But even amid a rise in his save percentage, Kepa has made three errors leading to goals already this term.
Mendy was signed on the back of a save percentage of 76.25% last season in Ligue 1, and that has risen since joining Chelsea to 80%.
According to Opta models, he has outperformed his expected goals conceded [xG] metric whereas Kepa has let in an extra 1.1 goals by the same measurement.
The statistics back up the initial impression that Chelsea now have a goalkeeper who has dramatically improved their chances to put together the wins they need to satisfy growing expectations.
Indeed, Mendy is the first goalkeeper since Petr Cech in 2004 to secure three clean sheets in his first three Premier League games for Chelsea. That is a fitting comparison as Cech made the same move from Rennes to Chelsea to become arguably the club's greatest-ever goalkeeper.
Cech has since re-joined the squad as an emergency goalkeeper and is now training alongside Mendy having offered his recommendation to transfer chief Marina Granovskaia to add the new No.1 to the squad .
Time will tell, but Chelsea are hopeful that their latest addition from Rennes will continue to compare favourably to their last.