Manchester United defenders Nemanja Vidic and Wes Brown are set to miss Sunday's Community Shield clash against Chelsea at Wembley.
Serbia centre-back Vidic and England right-back Brown missed Wednesday's 2-0 friendly win over Valencia at Old Trafford and neither are expected back this weekend.
John O'Shea is likely to fill in for Brown, who has a thigh injury, while Jonny Evans will replace Vidic, who is struggling with an ankle problem.
The United manager is hoping both will be fit for his team's Premier League opener against Birmingham on August 16.
As well as defensive worries, Ferguson had to admit Michael Owen's finishing had been disappointing against Valencia after he missed four chances to score his first goal at Old Trafford.
"It would have been nice for Michael to score - he deserved one," Ferguson said.
"He probably should have had four. He showed marvellous movement at times and when he took that great pass from Wayne Rooney, he put the ball over the keeper but just past the post."
While Owen struggled in front of watching England coach Fabio Capello, Ferguson was delighted with the performance of Ecuador winger Antonio Valencia, who set up both United's goals against Valencia with excellent crosses.
"It was a very exciting performance," Ferguson said. "It was a real winger's effort. He showed great speed, power and balance.
"Coming to our club he has immediately taken on the challenge and we are very pleased with what we have seen from him so far."