Sir Alex Ferguson estimates Rio Ferdinand will be out of action for two weeks after missing Manchester United's victory over Birmingham City. Ferdinand was forced to pull out with a thigh injury, with Ferguson claiming before the game that his £29.1m defender will be going for a scan in the morning.

However, the United manager has now put a timescale on the problem, which would make the 30-year-old a doubt for England's 2010 FIFA World Cup South Africa™ qualifier with Croatia on 9 September.

"I would imagine Rio will be out for two weeks," said Ferguson.

Ferguson also backed Wayne Rooney to top 20 goals in the Barclays Premier League this season after he grabbed the winner at Old Trafford. The United manager said: "We had some good opportunities and played some good football and in general I am satisfied with the result.

"Is Rooney capable of 20 plus Premier League goals? He is capable of that without question. You always need two or three of your strikers to get over the 20 goal mark," he said.

"It has always been an advantage over the years for us and Wayne is capable of doing that."

Opportunities for Owen
Meanwhile, Ferguson confirmed Michael Owen will have chances to start for United in the coming weeks. Owen came off the bench in the second half and only a fine save by Blues goalkeeper Joe Hart denied him his first league goal for the Red Devils.

"Owen made a great run and the keeper made a great save. But he will get his goals, no question about that," said Ferguson. "I started with Rooney and Berbatov today quite simply because they were at the club last season and were regular players and you've got to give them an opportunity.

"Michael will get his chances. There is no question about that," he said. "There are plenty of games coming up in the next few weeks to give him his opportunity and he will take them."

Rooney was also pleased to make a winning start, saying: "I thought at times we played some good stuff. Birmingham sat back in the first half and made it difficult for us, but we created enough chances to win the game.

"We couldn't get that second goal. They defended well. The second goal would have killed the game off, but at 1-0 there is always a chance of the other team getting a result."

McLeish upbeat
Despite the narrow defeat, Birmingham manager Alex McLeish took plenty of positives from his side's performance against the defending champions. He said: "On another day we may have taken something from the game.

"I know United had a couple of chances and Sir Alex will be talking about the ones they missed. But it is the most we have created here, certainly from my experiences here. I was disappointed we didn't quite nail one of the chances.

"We worked hard and the organisation of the team was great and they applied themselves brilliantly within the system," said McLeish.

"They showed they are a team that never gives up."