Chelsea need a right centre-back - can Koulibaly play there?
Kalidou Koulibaly has completed a move to Chelsea as the West London side quickly wrapped up talks with Napoli over a transfer for the Senegal international.
Koulibaly, 31, was wanted by Chelsea during the Maurizio Sarri days, but the Blues saw their efforts to sign him a few years ago knocked back by Napoli.
However, with just one year left on his deal in Naples, the Italian side weren't in a position to reject the €40 million move that has now happened.
Koulibaly has become Chelsea's first defensive purchase of the summer as they look to replace both Antonio Rudiger and Andreas Christensen.
The former has joined Real Madrid, while the latter has departed for Barcelona, both on free transfer after their contracts at Stamford Bridge expired.
Koulibaly won't be the only centre-back acquisition made by Chelsea this summer as Tuchel aims to add at least two new faces in a problem position group for him.
As well as the exits of both Rudiger and Christensen, club captain Cesar Azpilicueta has also reportedly asked to leave Stamford Bridge in order to join Barcelona, but the Spaniard won't be allowed to depart until a replacement is signed.
Matthijs de Ligt and Jules Kounde have both been heavily linked, but the former is set to join Bayern Munich, while talks with the latter seem to have died down amid interest from Barcelona.
As a result, Nathan Ake even emerged as a target, but the Blues have been thwarted in their efforts as the league champions rejected the move.
It was believed that Manchester City was to sign a replacement for their Dutch defender before selling him, but have now denied the move overall.
However, a problem for Tuchel is that Ake, as a left-footed player, would have suited the left-centre-back role in his currently deployed 3-4-3 formation. But, that position is also where returning loanee Levi Colwill would naturally fit in should he be given a chance, and would also be Koulibaly's best position.
Despite being right-footed, Koulibaly has featured solely on the left of a back four during his time at Napoli, with his strong weak foot playing a part in that.
Due to that attribute, Koulibaly would naturally be a Rudiger replacement, but with Chelsea looking at another player for that position, it may mean the Senegal man is needed on the other side.
As a result, Koulibaly may be stationed on the right of Tuchel's back three. The German head coach may switch to a back four, with Koulibaly and Thiago Silva the first-choice pairing, while a future signing provides cover at centre-back and left-back, but if he sticks with a back three and signs the pair, Koulibaly may be shifted to the right.
Can Koulibaly play on the right?
The Senegal international is one of Europe's most experienced defenders, so you would imagine that playing on the right wouldn't trouble him too much.
Add that to the fact that he's right-footed and that would suggest playing as Tuchel's right-centre-back wouldn't be of too much trouble to Koulibaly.
However, he's always played as a left-centre-back in a back four, so moving to a different flank in a different system may prove tricky.
In fact, Koulibaly has played just two of his last 148 Serie A games in a back three, so Tuchel may look to switch to a back four because otherwise it will take Koulibaly a period of adaption.
Playing on different sides of a backline is far more tricky than many would imagine, but Koulibaly is talented and experienced enough to adapt to the process well.
There's no indication that he'd be a success at right-centre-back, but there's no evidence he wouldn't either. Tuchel would be taking a risk to move such an established player away from his best position, but it's perhaps a risk worth taking if he views Koulibaly as a better option than Jules Kounde in Christensen's former role.