The Red Devils have started their Premier League campaign with a makeshift defence, but the Old Trafford boss is confident that his squad will be at full strength soon enough
The 33-year-old defender missed the opening match of the season on Monday - when the Red Devils lost 1-0 to Everton - with a groin injury.
Despite Ferdinand being ruled out of Saturday's home game with Fulham, the Old Trafford boss is hopeful his back four will look less makeshift against the Saints.
"Defenders have been having more injuries than the forwards in recent years," Sir Alex told United’s official website. "It is strange. You would think it was the other way around.
"We have a strong squad and we are going to use it. There will be opportunities for everyone to share in that and contribute to whatever we achieve this season.
"Phil Jones has started training. Chris Smalling is long term. Rio, I think, will be ready for next week.
"[Jonny] Evans was doing well but felt it in training on Sunday and hasn't trained since. I'm not sure whether that is long term or a short-term setback.”
Wide midfielder Antonio Valencia filled in at right-back in Monday’s loss at Goodison Park, but the United manager insists Rafael will more than likely be back in the position soon enough.
"Valencia can play anywhere," Sir Alex added. "He's a typical South American. He just loves playing. He is powerful and quick and can tackle. He can do most things. [Playing at right-back] is only short term.
"Rafael had been at the Olympics and had just come back but Antonio had been with the squad all the time and had been right-back on the tour."