from memory, Pep's league cup teams usually start more second string and get stronger as the tournament progresses. Palmer played a full 90 (?) away at Burnley in the same round last season, and i do think he'll play again at West Ham.
this is our cup! i think Foden & Bernie will be rested, Mahrez, Sterling & Torres all to feature. I'd go something along the lines of
Stefen
Walker/Egan-Riley - Stones - Ake - Zinchenko (is he fit?)
Fernandinho
Palmer - De Bruyne
Mahrez - Torres - Sterling
Any on the bench