Pogba and De Gea miss Man United training
Pogba has not played since September 30 due to a toe injury but there had been suggestions he could be fit for the clash in Serbia.
De Gea starred in United's 1-1 Premier League draw with leaders Liverpool on Sunday but failed to appear for the open section of training at Carrington.
Luke Shaw, Nemanja Matic, Diogo Dalot and Axel Tuanzebe were also absent but there was some better news for boss Ole Gunnar Solskjaer with Jesse Lingard making an appearance following a spell on the sidelines due to a hamstring problem.
United lie second in Group L, level on points with Partizan, after a win over Astana and a draw with AZ Alkmaar.