Thomas Tuchel’s Chelsea are currently flying high at the top of the Premier League — but a crisis could be closer than it currently appears.
Key to the Blues’ outstanding campaign so far has been their rock-solid defence, conceding only three goals in their 10 outings to date and keeping an impressive seven shutouts in the process.
Yet with a lack of depth, some shaky injury records and several expiring contracts, problems in the heart of their backline may not be far away.
We put the European champions’ defence under the microscope.
It is little wonder that Tuchel’s men have been so imperious at the back given the elite experience in their ranks.
At 37 years of age, Brazilian colossus Thiago Silva may have to manage his minutes more carefully these days but the former Paris Saint-Germain commander has not lost any of his class.
Starting half of the Blues’ Premier League outings so far this term, he brings the communication and composure of a man who has spent over a decade at the pinnacle of the sport.
Next to him is one of Europe’s most in-form defenders in Antonio Rudiger — the German international having proved a revelation since the arrival of his compatriot in the Stamford Bridge dugout.
That impressive duo are supplemented by Danish defender Andreas Christensen and club captain Cesar Azpilicueta, two seasoned internationals who have also played pivotal roles in Chelsea’s recent successes.
However, for a man who likes to operate with a back three, Tuchel is living a little dangerously in terms of his squad depth.
Given Azpilicueta operates more frequently on the right flank, the boss effectively entered the campaign with his three natural central defenders backed up by two youngsters — Trevoh Chalobah and Malang Sarr.
Chalobah, 22, must have been as surprised as anyone when featuring in the UEFA Super Cup against Villarreal back in August but has taken his opportunity with both hands.
The Blues have conceded only once in his five Premier League starts this term, with the academy product producing some fine performances and even netted a spectacular goal against Crystal Palace on his first league start.
Sarr, meanwhile, has so far been restricted to one league appearance and two Carabao Cup starts, though his Premier League bow was in a 1-0 win away at Brentford.
While the Blues have negotiated the first quarter of the campaign without any issues, things are unlikely to be as rosy throughout the entire of 2021-22.
Silva only managed 23 top-flight appearances last term and a similar number is likely his target again, while Christensen has only featured in an average of 17 matches a season across the last three years.
What is more, Azpilicueta’s appearances are now being more carefully managed and, while Rudiger is a near ever-present, an injury to him would leave the Blues suddenly looking awfully exposed.
Though Chalobah and Sarr did help Chelsea to a clean sheet at Brentford last month, they needed a fair chunk of fortune to do so after the Bees hit both posts while also forcing a late string of sublime saves from Edouard Mendy in the away goal.
They were outshot by their fellow Londoners by 17 to five, while losing 35 out of 52 aerial duels in the contest — numbers that would not bode well if repeated over an extended period.
The other elephant in the room is the uncertain futures of Chelsea’s central defensive options.
Remarkably, four of the six aforementioned stars will see their current contracts run out this summer, with only Sarr — the least-used of the bunch — tied down for the long-term.
While agreements seem inevitable for young Chalobah and the popular Azpilicueta, questions will be asked over the logic of extending veteran Silva’s stay much longer.
Christensen looks bound for pastures new and is thought to be attracting interest from the likes of Juventus and Atletico Madrid but it is the potential departure of Rudiger which is of greatest concern.
Unable to agree an increased wage with the Blues as of last month, negotiations are reportedly on hold and Real Madrid hope to swoop for his services on a pre-contract agreement as early as January.
Even if some of those deals are successfully extended, new arrivals will be required at Stamford Bridge pretty quickly.
Many fans were left baffled by the permanent departures of Kurt Zouma and Fikayo Tomori this summer but their sales do at least suggest that cash is available for Tuchel to bring his own men in if required.
Sevilla and France defender Jules Kounde has been linked strongly for several months now.
And another high-profile star touted for a move is Juventus’ Dutch defender Matthijs de Ligt, who could be allowed to leave Turin for around £85million if recent reports are to be believed.
Both aged just 22, moves for the pair will cost a pretty penny — but they would also mark the capture of two of Europe’s most exciting defensive talents.
In the face of frequent questions about his defensive stars, Tuchel has consistently opted to keep his powder dry.
However, it is clear that he would be delighted to continue to work with what he currently has at his disposal in an ideal world.
Speaking last week, he said: "Christensen is very strong, very reliable and he has not reached his limits because at his age there is still room to improve.
"He can be a top defender for us in the next years and hopefully he will be because he comes from the academy.
"I hope that they [Christensen and Rudiger] find solutions — but it's not only between coaches and players, and what we wish for. We hope that they find the solution."
For all their success on the pitch at the moment, Chelsea’s most important work in the coming months may be done in the boardroom.