Michael Carrick and Ryan Giggs both limped out of the opening-day draw with Newcastle and the Mancs have already suffered a blow in the Championship race because Newcastle could have nicked all three points.
Obafemi Martins put the Magpies in front, before Darren Fletcher equalised for the Premier League champions.
But the Red Devils lacked ideas as Newcastle pushed them all the way.
Ferguson: "Michael suffered a bad blow to his ankle.
"It was pretty swollen and didn't give him any time to recover. He will be out for two or three weeks.
"Ryan hurt his hamstring, so we had to bring him off as well - which between the pair of them, meant we lost experience at vital moments in the game.
"We have a good squad. Carlos Tevez will come back next week and he and Wayne (Rooney) will be my strikers.
"We have shown before we can come from behind.
"There are 37 games left, so this is not a disaster.
"I did not expect to lose a goal at a set-piece to a header from a guy who is 5ft 8in.
"Once we got the equaliser, I thought we would kick on. But while we were the better team, they were always a threat on the counter-attack - and we have to take into account the personnel we have missing."