The Manchester United loanee had been a regular in the Premier League XI after joining the club, and sat out the win over Panathinaikos on matchday two, but then saw his place taken by Pedro Neto in the victory over Newcastle United.
Sancho would have likely started in the cup game with the Magpies a few days later, but was then struck down with illness, and the 24-year-old was ineligible to face his parent club on Sunday.
With Neto now a regular in the league side, that means Sancho may have to work his way back into the team by performing well as part of manager Enzo Maresca's cup XI.
The Chelsea boss has often made 11 changes to his side when playing in Europe or the EFL Cup, as the Blues' inflated squad allows for such heavy rotation, and a way of keeping the bulk of the squad happy.
Elsewhere, goalkeeper Filip Jorgensen and French centre-back duo Axel Disasi and Benoit Badiashile have played in every cup game this season, and this should be no exception.
The return of Reece James from injury has seen Marc Cucurella demoted to cup football though, and the Spanish Euro 2024 winner may start again here as he did against Panathinaikos.
After a high challenge from Lisandro Martinez on Sunday, Cole Palmer took precautionary measures to protect his knee post-match, and not being in Chelsea's Conference League squad will allow him time to rest ahead of the clash with Arsenal at the weekend.
Along with Palmer, most of Chelsea's first-choice options are set to be left out entirely, as James, Moises Caicedo, Wesley Fofana, Malo Gusto, Nicolas Jackson and Romeo Lavia have not been in the squad for either of their last two cup games.
Despite costing Chelsea £105m just under two years ago, Enzo Fernandez has now found himself out of the team, and relying on minutes in this competition alongside Kiernan Dewsbury-Hall in midfield.
There is an abundance of expensive talent ahead of Enzo too, with the four goals against Panathinaikos being scored by Mykhaylo Mudryk, Joao Felix and Christopher Nkunku, who are all set to start.
Chelsea possible starting lineup:
Jorgensen; Renato Veiga, Disasi, Badiashile, Cucurella; Enzo, Dewsbury-Hall; Sancho, Joao Felix, Mudryk; Nkunku