Injuries and suspensions at the end of last season meant that Roberto di Matteo was not forced to choose his first choice centre-back pairing, rather just selection whoever was available.
At one point, including the FA Cup Final, Jose Bosingwa was played in central defence, and while their first choice trio were all fit for the Champions League Final, John Terry was suspended meaning Di Matteo partnered Cahill and Luiz, but also was spared the tough decision of having to leave one out.
This season that rotation has continued, but not through choice, rather need. Terry and Luiz were selected for the Wigan match, indicating they would be his first choice, only for Cahill to step in for the injured Luiz against Reading and prove his worth by scoring an excellent goal.
John Terry's injury kept him out of the Newcastle game - with Luiz and Cahill forming the club's third defensive partnership in as many games.
Now the situation is likely to get even more complicated, thanks to the arrival of Cesar Azpilicueta. The Spanish right-back has signed from Marseille to play, and not sit on the bench.
But how can the in-form Branislav Ivanovic be left out? The Serb may play alongside the new arrival, as he may now be considered for a centre-back spot as well, the position for which he was originally signed to play.
This would mean four players battling for two spots, although Ivanovic is still likely to feature in his fair share at right-back too.
With Ryan Bertrand impressing, and ultimately wishing to displace Ashley Cole as Chelsea's left back, the club's defence has a bit of a transitional feel about it.
Chelsea could conceivably have a first choice defence of - Cech - Ivanovic - Luiz -Terry - Cole - and a possible future one of Courtois - Azpilicueta - Cahill - Hutchinson - Bertrand
Courtois and Hutchinson are out on loan at present, but Chelsea fans see them, especially the Belgian goalkeeper, as an integral part of the club's future.
But for this season, Di Matteo still has decision to make, Azpilicueta or Ivanovic at right-back, and who are his two best central defenders?
Eventually they will have to find a settled backline, as that can only benefit goalkeeper Petr Cech, and the team as a whole going forwards. The question is, who should it be?
Who are your first choice centre-back pairing? Who should play at right-back? Should Ivanovic move inside?
image: © Ronnie Macdonald