Wingers Antonio Valencia and Nani will miss Saturday's trip to Reading.
Although Valencia is expected to return for the derby with Manchester City, Nani will be sidelined for at least another month.
Nick Powell and Ryan Giggs should be fit enough to be considered for the weekend and Nemanja Vidic has started training as he bids to make his comeback soon, possibly as early as Wednesday against Cluj. Rio Ferdinand will return to the starting line-up after being rested for the win against former club West Ham.
"Nani and Valencia are still out," confirmed Sir Alex. "Nani will be out for four or five weeks. It's a hamstring injury and you have to take your time with it.
"Antonio should be fit for next week. He's got a hip injury, which is painful, but getting better.
"Nick Powell has had a virus but should be okay for tomorrow and Giggs had a slight hamstring strain but should also be okay. Nemanja Vidic has started training, which is good news, and Paul Scholes is back from suspension. It's quite late for Scholesy to get a suspension - it's usually about October!"
"It’s amazing that we’ve had defensive injuries for such a long period and now we’ve got the defenders back we’ve got two wide players injured. That’s the game for you. Everyone else is fine."
Although Reading are favourites to go down, the boss expects a difficult game against Brian McDermott's Royals.