Since the full-time whistle blew in Frank Lampard's first game as Chelsea head coach and the Blues were wondering how they had just shipped four goals against Manchester United, questions have been asked over the boss' ability to organise a defence.
It's a concern which has been answered somewhat this season with the signing of Thiago Silva, the 36-year-old Brazilian who joined on a free transfer from Paris Saint-Germain and immediately turned Chelsea into one of the meanest defences in the Premier League.
Unfortunately, because of his age and declining physical fitness, he can't be relied upon to play week in, week out - particularly after leading PSG to the Champions League final late into the summer with very little recovery time - and he looks set to be rested for Saturday's trip to Newcastle United.
Lampard's side have conceded just one goal in their last six games, five of which Silva was a part of. He sat out the comfortable 4-0 win over Krasnodar, but his only absence in the league came as Chelsea capitulated against Southampton.
Chelsea shipped three goals with a centre-back pairing of Kurt Zouma and Andreas Christensen, but they did also have the error-prone Kepa Arrizabalaga in goal. Fortunately, the Spaniard has since been replaced by Edouard Mendy, who has done more than his fair share when it comes to strengthening the Blues' back line.
It means the only test of a Silva-less Chelsea side (with a reliable goalkeeper) was a team who are closer to the relegation zone in the Russian Premier Liga than they are to the league leaders and who managed just 29% possession on the day they faced the Blues. With all due respect, that's hardly the biggest threat.
Saturday's meeting with Newcastle looks set to answer a lot of questions.
How reliant upon Silva are Chelsea? How important is Mendy? Has Lampard actually done anything or is this run of success all on his new signings?
There's reason to believe that Lampard has been putting in the work. Chelsea's approach to defending set-pieces is far superior than last year, when only Ligue 1 strugglers Amiens conceded more goals from corners than the Blues. Changes have clearly been made on the tactics board.
However, there will undoubtedly be a reliance on Silva, whose role as an on-field general is irreplaceable at times. Just ask PSG.
While the Ligue 1 champions have predictably continued to steamroll the competition at a domestic level, their record of two defeats from three Champions League games definitely gets alarm bells ringing for a side who were playing in the final of the competition just a few months ago.
The introduction of Abdou Diallo or Danilo Pereira has not made up for the loss of Silva, and it remains to be seen who will be given the chance to compensate for the Brazilian's omission at St James' Park.
On paper, you'd assume it'd be Antonio Rudiger who will step in. The German has been playing in the Champions League and has been the first reserve in the Premier League for the last three games, so he seems like the most-likely candidate for a cameo appearance here.
Rudiger's involvement would create its own little subplot. St James' was the scene of one of the defender's biggest crimes last year when he inexplicably ducked to allow Isaac Hayden to bundle home a 94th-minute winner when the two sides met in January.
If it is Rudiger who plays, it will be down to the German to make up for his error last year and prove that he still has what it takes to lead Chelsea's defence, and he'll be constantly compared to Silva, the actual leader, while he does so.
All of this defensive uncertainty will come on a ground at which Chelsea have managed just one victory since 2011, and even that sole triumph came courtesy of an 87th-minute own goal from DeAndre Yedlin. Chelsea just don't like St James' Park.
The Blues don't have any time to think about that record or fret about playing without Silva. Their claims that they have sorted out their defence are on the line. It's time to see whether Lampard has made Chelsea better, or whether he's added a 36-year-old defender to do that job for him.