For two games last month, Patrice Evra was their only orthodox defender and central midfielders were also in short supply as Darren Fletcher, Tom Cleverley and Anderson were all out of action.
The problems are easing slightly, especially now Paul Scholes has come out of retirement, although the Red Devils do have doubts over Chris Smalling and Phil Jones heading into Saturday's Old Trafford encounter with Bolton.
But Ferdinand believes the fact United can move level with table-toppers Manchester City by winning the north-west derby emphasises their durability.
"We don't like making excuses but look at the team we put out against Blackburn," said Ferdinand.
"You see a lot of people moaning about their squads because the transfer window has just opened.
"But if you took the amount of players we have had out to any other squad in the league, they wouldn't be sitting where we are now.
"That speaks volumes for our squad.
"That is why when I am in the changing room I am more than happy with the people I see around me."
Bizarrely, though United are looking to avoid a third straight Premier League defeat, it is City who are on the back foot heading into the weekend fixtures after two losses in cup combat - while Tottenham have loomed up as a third challenger.
It is rare for the Red Devils to be lining up for the run-in against such inexperienced contenders. But the aims do not change.
"You always know there will be ups and downs during the season," said Ferdinand.
"We had a bad week the one before, losing two games, but there is no better game to come into than Manchester City.
"But I don't think we have the advantage now because of one result. It is too early to say.
"We are all round the same area and fighting for the same thing.
"You all have your peaks and troughs, hopefully Manchester City and Tottenham will experience lows that go on a lot longer, we can get a few players back from injury and push on."