England forward Palmer, midfielder Romeo Lavia and defender Wesley Fofana have been purposely left out to manage their workload.
Chelsea could play about 80 matches this season in five competitions.
The decision was made to rest star man Palmer in the league phase of Europe’s third tier competition, with Lavia and Fofana working their way back from long-term injuries.
Chelsea can re-register the trio for the knockout rounds on 6 February when squads can be re-submitted.
Young midfielders Cesare Casadei and Carney Chukwuemeka, and striker Marc Guiu have been selected in their place as the Blues look to spread minutes around fringe players in a competition they are strong favourites to win.
Left-back Chilwell, however, has been dropped and continues to be on the fringes at Stamford Bridge.
Manager Enzo Maresca has told the England defender he has no future at Chelsea and Chilwell has been offered to multiple Premier League clubs this summer.
Chilwell is unlikely to play for Chelsea again this season despite the club’s participation in the Premier League, Carabao Cup, FA Cup, Conference League and expanded Club World Cup in June 2025.
It is unclear if the 27-year-old will even train with Maresca’s first-team squad amid reports linking him with a move to Turkey where the transfer window remains open.
Chelsea have faced criticism for hoarding players during the transfer window, with 42 senior players on the books ar one point this summer.
Some have been sold, reducing the number to around 36 players, which includes some inexperienced academy players.
Meanwhile, Tottenham have left defenders Djed Spence and Sergio Reguilon out of their Europa League squad.
They could only name 23 players instead of the usual 25 because of a lack of club-trained options.
Spence is back in the first-team fold after loan spells at Leeds and Genoa, but Reguilon could leave the club.