The development represents a worsening of the initial prognosis, which had originally projected the Japan international to recover from his knee injury a month after aggravating it in late October. Kagawa had made a bright start to his career at Old Trafford following his summer switch from Borussia Dortmund, scoring two goals in his first six games.
But Ferguson told reporters ahead of the Red Devils' UEFA Champions League tie with Galatasaray that "His progress has been slow."
"He's done enough training to make sure his fitness is OK," the veteran manager declared. "I'm looking forward to bringing him back."
18-year-old Nick Powell will also feature, with Ferguson adding, "He's played in front of 76,000 as a substitute, but this will be his first European away game. It'll be a big day for him."