Ferdinand was not in the 19-man squad that flew to Portugal on Tuesday morning, meaning United were without their first-choice central defensive pairing as Nemanja Vidic is currently missing with a calf problem.
There was no place either for Federico Macheda or Mame Biram Diouf, who scored twice for the reserves in their win over Fulham on Monday night, but Jonny Evans and Patrice Evra shrugged off hip and knee knocks picked up at Bolton on Saturday.
It is not thought Ferdinand has suffered a fresh injury. However, after making his first appearance in a month during the 5-0 romp at The Reebok, and with Chelsea due at Old Trafford on Sunday, Sir Alex Ferguson is not wanting to take any chances with the 32-year-old, whose fitness record has been patchy over the past few years.
With Ferdinand out, it is likely to mean a move into central defence for Phil Jones, outstanding at full-back on Saturday, who would be making his debut in the competition.
Michael Owen, fresh from watching his horse Brown Panther finish second in the St Leger, was also named, although if changes are made to Ferguson's attacking line-up, last season's joint Golden Boot winner, Dimitar Berbatov, would appear to have more of a claim.
Ferguson has suggested he will rely on experience, which could be good news for Darren Fletcher, Park Ji-sung and Ryan Giggs, who have been reduced to peripheral roles so far this term.
The United boss must also decide whether to hand Anders Lindegaard his competitive debut, or stick with David de Gea, who has been steadily improving after a shaky start to his Red Devils career.
United (from): De Gea, Lindegaard; Evans, Evra, Fabio, Jones, Smalling; Anderson, Carrick, Fletcher, Giggs, Nani, Park, Valencia, Young; Berbatov, Hernandez, Owen, Rooney.