The underwhelming results that came right before Chelsea's new co-owners Todd Boehly and Clearlake Capital decided that a change in the dugout was necessary.
'I can't be the player everyone expects me to be from the first game, so I'll need time, he said. "I'll take my time, and in two or three months, I'll be the one everyone's waiting for," Kouilbaly said.
The fact that head coach Thomas Tuchel did not have time to wait was unknown at the time.
The underwhelming results that came right before Chelsea’s new co-owners Todd Boehly and Clearlake Capital decided that a change in the dugout was necessary were a notable subplot of the Senegal international’s steep learning curve in a new team, tactical system, and league after eight years in Italy with Napoli.
Under the German, he started six of the seven games, missing out the other one due to suspension.
However, Chelsea only managed one clean sheet in those contests, and Koulibaly’s assessment of his own readiness turned out to be more accurate than Tuchel’s expectations.
There have been enough instances of the team’s outstanding defensive instincts and ball skills to impress Graham Potter, the new head coach, but there have also been times when the 31-year-aggressive old’s tendencies and aerial fallibility have caused problems.
In reference to Todd Boehly, Gary Neville cautions Chelsea fans: “US investment into English football is a clear, present danger.”
Koulibaly has gushed about how much he enjoys facing off against individual attackers. Along with his speed and ease defending in space, his desire to dominate every opportunity makes him a natural fit for a high-pressing system. However, with such a proactive approach, any error could have a high cost.
Kouilbaly has already participated in a number of games and has now benefited from some great experience on how to improve his skills and what to add to them.
At that unveiling in August, a player who spent eight years in Naples and was selected four times for the Serie A Team of the Year described the main adjustment challenge to the Premier League as
"I have to think faster, go faster, and move my eyes faster.
“In Serie A, everything is more with the brain, calmer. You have to think of every movement. Here, you have to think very fast, and this is the first thing I have to change.”
Koulibaly will need to catch up quickly in that sense, Potter will be hoping.
Koulibaly’s time at Chelsea hasn’t exactly been terrible so far.
Beyond the stunning volley from a corner from Marc Cucurella that started the scoring, he displayed many of the qualities that can make him a tremendous asset to an elite team against Tottenham.
The game in which his technical ability with the ball at his feet helped Chelsea beat the Spurs press, pin them back, and play through their low block. He plays a role in shaping to play a pass with his left foot here, assessing his options as Dejan Kulusevski advances to stop the flow…
Koulibaly also managed to strike the ideal balance between sideways passes that were safe and incisive ones that took a number of opponents out of the game in the opponent’s half.
Koulibaly will undoubtedly have a lot to contribute to Potter’s team both in and out of possession once he modifies his instincts to the unique characteristics of Premier League football.
Chelsea’s set-piece defence under Potter should improve with the addition of fellow center-back Fofana from Leicester, but Koulibaly must demonstrate his impressive physical attributes in the air.
The most pressing task for Potter is to develop a tactical plan for Chelsea that makes the most sense in every area of the field, with a pressing system that enables them to defend from the front first.
Success or failure on defence is a team effort rather than an individual one.
However, there is strong evidence to suggest that a fully adapted Koulibaly would add more than he subtracts if Potter can find the right structure.