Koulibaly nearly joined Norwich, Liverpool were keen, but he struggled against Salah

Chelsea are the lucky club to get their hands on the defender, who captained Senegal to Africa Cup of Nations glory in 2022.

He leaves Napoli after eight years of service, however, if different decisions were made, Koulibaly's career would've gone in a very different direction.

A tough first season with the Serie A club led to speculation surrounding his future, with Norwich, who had just got promoted in the Premier League, trying to sign him in the summer of 2015.

"Some teams have tried to sign me, but Napoli said no to several offers, such as €15million (around £13m) from Norwich," Koulibaly later told L'Equipe.

"Maurizio Sarri believed in me, and this gave me a lot of confidence."

Sarri's belief paid off as Koulibaly developed into one of the world's best centre-backs.

"There's no doubt about the skills of the player, he improved a lot under Maurizio Sarri," Italian football expert Daniele Fisichella told talkSPORT. "His movement, his timings, his passing, he's very good on the ball.

"When Napoli were playing 'Sarriball', Koulibaly was as good a passer as Napoli's two best midfielders.

"Yes, he hasn't played too much in a back three, but he can read the game really, really well. He's very quick as well which will allow the Chelsea back line to play up the pitch, he's very good at defending very close to the halfway line.

"But Koulibaly's strength is perhaps in the box. All he does around the box and the way he holds his line and his decision-making, he has improved a lot."

Chlesea failed in an attempt in 2016, while a number of the Premier League's big hitters later took an interest in him with speculation surrounding his future taking hold from the summer of 2019.

Napoli managed to keep hold of their centre-back and put a price of £100million on Koulibaly to the likes of Liverpool and Manchester United, who were linked with him in January 2021.

It's no wonder Liverpool were linked with Koulibaly, who put on a number of impressive displays where he neutralised Mohamed Salah and Sadio Mane in Champions League clashes against the Reds at Napoli's home in 2018 and 2019.

However, Salah got the better of him when the Serie A side went to Anfield in 2018, the Egyptian ghosting past Koulibaly before slotting the ball past David Ospina - the goal securing Liverpool the win they needed to reach the last-16 of the Champions League en route to winning the competition.

Koulibaly also ran into some difficulty when Salah was at Roma, having been dispossessed by his opponent, who laid the ball onto Edin Dzeko to score in a 3-1 defeat for Napoli in October 2016.

Another player who Koulibaly has struggled against is Dejan Kulusevski, who's currently on loan at Tottenham from Juventus.

The Sweden international had a loan spell at Parma in the 2020/21 season, scoring an 87th-minute winner from the penalty spot when he was felled by Koulibaly in the box after beating the defender when cutting inside.

And in a key early season game against Juventus in 2019, the centre-back had a night to forget too.

Juventus beat Napoli 4-3 thanks to a late Koulibaly own goal and earlier in the game he was easily turned by Gonzalo Higuain for another goal, showing he's not always a colossus at the heart of defence.

But everyone's human and Chelsea fans will rest a lot easier knowing they'll have Koulibaly at the heart of their defence for the coming years.