Man United quartet miss training
Danny Welbeck and Tom Cleverley were absent as well as central defenders Nemanja Vidic and Rio Ferdinand.
Cleverley, Vidic and Ferdinand all missed the weekend's 1-1 draw with Southampton in the Premier League.
Adnan Januzaj took part in the training session after being added to the Champions League squad as a home-grown player.
Ferdinand and Vidic both missed Saturday's game with minor knocks and United manager David Moyes had hoped that either or both would be fit for the midweek visit of Spanish side Real Sociedad.
Cleverley has been out with a calf injury, but it is not yet known why Welbeck was absent from the training session.
The session did feature Darren Fletcher taking part with the whole group after several weeks working on his own to regain fitness.
The 29-year-old midfielder has been battling a chronic bowel condition and has made only seven starts in the past two years - his most recent was on Boxing Day last year - but there are hopes that he could return to competitive action later this month.
United should go into Wednesday's match against Sociedad full of confidence as the Basque side have struggled in the Champions League, losing both their opening games, 2-0 at home to Shakhtar Donetsk and 2-1 at Bayer Leverkusen.