Kalidou Koulibaly is officially a Blue. The 31-year-old brings a ton of experience at the centre-back role and will no doubt be an immediate starter for the club.
Here are two ways the Chelsea defence can line up next season with Koulibaly signed.
Option 1: Switch to a back four
Koulibaly has played as the left centre-back for most of his Napoli career, operating in a back four. While Thomas Tuchel prefers to play three centre-backs, he did revert to the usual four-man defence a few times last season.
Koulibaly and Thiago Silva, on paper, are arguably the best defensive partnership in the Premier League. Their combined experience is definitely far ahead of any other duo in English football.
Option 2: The usual three-at-the-back
Tuchel recently commented on how he felt that Rudiger-Silva-Christensen was the best back three in the world. The manager also added that Chelsea want to sign two more centre-backs.
In that case, we are more likely to see Chelsea playing the same three-at-the-back formation, with Reece and Chilwell the wingbacks.
As of now, Trevoh Chalobah is the best man to play the third centre-back. That could change, if someone like Presnel Kimpembe is brought in.
Regardless of another new defender, however, the core of Silva and Koulibaly is indeed a very exciting prospect - Premier League attackers beware!