Both central defensive pillars Nemanja Vidic and Rio Ferdinand were substituted in Sunday's 2-1 win at West Brom while right-back Rafael had previously joined left-back Patrice Evra on the sidelines after dislocating his shoulder in training on Friday.
Evra should be back for the clash with Tottenham but Ferdinand will be out for around a month-and-a-half, thus presenting more opportunities for the younger defenders in the Reds' ranks.
"We've had a torrid two or three days," Sir Alex admitted. "Rafael hurt his shoulder in training and is out for 10 weeks as he's going to need an operation.
"Rio has hurt his hamstring and will be out for six weeks. With Vida, we don't know whether it's a nerve problem or not. He'll have that checked tomorrow. He had a calf problem prior to the game and could be out a couple of weeks. But with Chris Smalling, Jonny Evans and Phil Jones here, it's a godsend to be honest with you. Also, Patrice Evra will be back next week, he'll be fit, so I've got options.
"I must say Phil and Jonny did very well and Chris is playing right-back at the moment so we'll get through."
Sir Alex was speaking to Sky Sports and MUTV.