Defender Trevoh Chalobah, who was recalled from his loan at Crystal Palace last month, is included. New signing Mathis Amougou, who joined the Blues from Saint-Etienne on deadline day, has also been included.
This is while French center-back Wesley Fofana and Belgian midfielder Romeo Lavia remain out, having also not played in the league phase.
Axel Disasi, Renato Veiga, Carney Chukwuemeka, Cesare Casadei and Joao Felix, who all left Chelsea in January, have all now dropped out which leaves room for Palmer who is yet to make a European appearance for Chelsea.
Chelsea are favourites to win the Conference League but will not play their last-16 tie until March. The introduction of Palmer means he will be earning more minutes for the side under manager Enzo Maresca who clearly believes he is necessary for latter stages of the tournament in which they have cruised through so far.
Maresca’s next opponents will be one of Gent, Real Betis, Copenhagen or Heidenheim and with the addition of the 22-year-old English superstar they are likely to continue their European dominance.