The move from a back-three to a back-four comes with numerous challenges, but is vital if Maurizio Sarri wants to impose his philosophy on Chelsea.
The two centre-backs in a back-four have to be both capable defenders and – in Sarri’s system – excellent ball-players.
And, despite their vast resources, Chelsea have struggled to find world-class central defenders ever since the departure of John Terry.
Kurt Zouma has never convinced, David Luiz has clear flaws as a defender, César Azpilicueta will move back to his preferred right-back and both Gary Cahill and Antonio Rüdiger lack the ball-playing ability to suit Sarri.
Andreas Christensen is probably the only centre-back that has both the required technique and defensive nous to fulfil Sarri’s requirements.
So, with a centre-back-shaped hole glaring, is it time to give 17-year-old Ethan Ampadu a chance in the first team?
Having made his professional team debut for Exeter City at the age of 15 years, 10 months and 26 days, Ampadu has been part of the Chelsea first-team set-up for over a year now.
Initially a central midfielder, Ampadu has found his preferred position at centre-back where he has had the opportunity to showcase his defensive solidity and ball-playing skills.
The Welshman – seen to Welsh fans as a key building block for the future – has displayed maturity beyond his years in his few appearances, which could convince Sarri to give him a shot.
Chelsea's best player on the pitch is a 17-year-old Welshman. Their best player in the Community Shield was 17. Please don't loan them
— Will Pearse (@wfhp408) August 7, 2018
And, with the uncertainty in defence, he could do worse than handing Ampadu a run in the starting XI.