The lifting of Chelsea’s transfer ban last month left many Blues fans wondering about who they could possibly sign this January. It was almost like a fantasy booking thing, with fans asking for the likes of Jadon Sancho to join this very month. But with ten days to go for the window to close, Chelsea haven’t made a single signing. But the position they need to improve the most in is the centre-back position.

Perhaps, that became clear in the club’s recent 1-0 loss to Newcastle United at the St. James’ Park. Isaac Hayden did grab a last-ditch goal against the Blues, whose fans were left to criticise Kepa Arrizabalaga for failing to keep the ball out. But the Spaniard was left to lecture Antonio Rudiger for not closing the Magpies midfielder down well enough.

And he had a point. The German couldn’t deal with Hayden in the lead-up to the goal. And it exposed Chelsea’s defensive issues once again. Head of Sport at Topp Casino, Josefin Bjorklund, commented: “It’s Martingale theory really, isn’t it? Chelsea clearly need a dominant central defender!”

So far this season, the Blues have let in 30 goals in the Premier League. That is as many as Wolves, one less than Tottenham and only two less than Arsenal. It is also only one less than Brighton. While that isn’t a good sign, they have underperformed on their XGA by 4.40- a sign individual errors like the Rudiger one are letting them down.

The Hayden effort at the weekend had an XG of 0.34. That isn’t as huge a chance as the poor defending made it look like. That has pretty much been the story of their league campaign. And if not for the teams below them being as inconsistent as them, Chelsea may well have been out of the top-four by now.

The club has let in only 15 goals from open play this season- the third-best record in the division. But they have let in seven goals from set-pieces and that is the tenth-best in the league and as many as Watford. They are also the fourth-worst team when it comes letting in goals on the counter-attack.

All these numbers don’t make for good reading at all. It is a department that the club needs to strengthen in, as the season wears on. And that is probably why links with Bournemouth defender Nathan Ake came up in recent weeks too. But the club pulled out of the deal and it doesn’t seem to be happening now.

As things stand, Chelsea have four CB options. Kurt Zouma has made 18 appearances, while Rudiger has made eight of them. Andreas Christensen has made ten appearances, with Fikayo Tomori having made 14 of them too.

There is depth in that team. But there is no one defender who stands out from the bunch. There isn’t a constant pairing that can play in every game. Like Virgil van Dijk for Liverpool, Toby Alderweireld for Tottenham, Caglar Soyuncu for Leicester or Harry Maguire for Man United, there isn’t one defender who can stand out from that lot.

That defender has to be someone who elevates the team to the next level and establish the team as a title contender. Reports have linked the club with Napoli’s Kalidou Koulibaly and that is the level the club should be looking at, in an attempt to improve the defence.

Napoli owner Aurelio de Laurentiis has high praise for the Senegalese defender and he’s never shy to admit it. The film producer once told ESPN (Via BR): “He has a clause of £150m. But, for example, in England, they paid £85 million for a player. In Napoli, I would pay £30-£35 million. With that in mind, I think Koulibaly’s value is £250 million if they paid that much for that guy.”

While that valuation is certainly lofty, but that is what Lampard should aim for. Over the next few years, the likes of Tomori and Zouma might reach another level. But that is a long way to go. A defender like Koulibaly should be made a priority in the summer transfer window.