Ferdinand is now a doubt for England's fixtures against Slovenia and Croatia next month after being sent for a scan on the thigh injury which ruled him out of the Birmingham game.
Evans, a pre-match doubt with an ankle knock, was substituted in the second half after suffering a recurrence of the injury and United manager Sir Alex Ferguson admits that selection problems are mounting in the build-up to the match at Turf Moor.
Ferguson said: "Ferdinand will be out for probably two weeks and that's a bit of a blow for us. Evans is injured again, while Gary Neville has only just started training, and Rafael da Silva is still missing with his dislocated shoulder.
"We have been having a hard time with defensive injuries over the last two years, but people are capable of coming in for us.
"Wes Brown hasn't had much training and Ritchie De Laet, who was on the bench today, will figure now. Nemanja Vidic (calf) is back in training and that's good news. He should be back for Wigan away on Saturday."
Despite dominating possession, United had to rely on Wayne Rooney
's first-half goal to secure the three points.
Ferguson said: "Wayne is off to a flying start and he took his goal well. His initial header was a good one, but he reacted the right way by following up for the rebound. With his goal in the Community Shield last week, hopefully he is on the road to getting a significant total for us this season.
"He is capable of getting more than 20 goals for us. We know it's not impossible for the boy and hopefully he will do that."
Birmingham manager Alex McLeish claimed he was heartened by the performance of his promoted team against the champions.
"Sometimes even a narrow defeat can enhance confidence, strange as it may seem. I am very encouraged by the way we played." McLeish said.
"You always worry that, if you come here and try to frustrate them and lose an early goal, Plan A is out of the window. But the players deserve enormous credit for hanging in there."
United substitute Michael Owen should have made it 2-0 in stoppage time when, after beating the offside trap, he shot straight at goalkeeper Joe Hart, but Ferguson expects the former England forward to score his first competitive goal for United quickly.
He said: "The goalkeeper made a great save from Michael. But I'm sure he'll get his goal and, once he does, it will set him on the road."