Ferguson's central defensive stalwarts both limped off during the second half of the first game of United's Barclays Premier League title defence.

Ferdinand appears the most serious, sidelined for six weeks with a hamstring problem that also means he will miss England's Euro 2012 double-header against Bulgaria and Wales next month, as well as the start of United's latest Champions League quest.

"Rio has a hamstring injury. He will be out for six weeks," said Ferguson.

"With Nemanja, we hope it is a nerve in his calf.

"He felt it prior to the game but he wanted to play. That may be a couple of weeks."

With young full-back Rafael ruled out for 10 weeks after dislocating his shoulder in training, Ferguson suddenly has a worrying list of defensive problems ahead of a difficult start, that now pits his side against Tottenham and Arsenal at Old Trafford over the next fortnight.

The bright spot for Ferguson is the anticipated return of Patrice Evra from a knee injury against Spurs next Monday.

"We can always put Fabio on the right if we need to. We also have Chris Smalling, so we will get through," said Ferguson.

Aside from the joy of taking three points on an opening weekend when Liverpool, Arsenal and Chelsea all failed to win, it proved to be a difficult day for United.

New £18million goalkeeper David de Gea was in the spotlight's glare, encountering difficulties dealing with the traditional high balls into the box and compounding those anxieties by diving clean over the top of Shane Long's strike from an acute angle, gifting West Brom an equaliser which they had not looked like getting up to that point.

It does seem United have plenty of work ahead of them in order to get the 20-year-old battle-hardened and physically up to the demands of life in England.

However, Ferguson is adamant he will cope.

"He is young. He will learn. He will come through," said the United boss.

"David's concentration cost him the goal. It was a slack goal to lose but it is an experience for the lad.

"I couldn't believe he never got a free kick in the second-half. The aerial assault on him was ridiculous.

"It was the same when Peter Schmeichel came. They punished him in his first few games against Leeds and Wimbledon. They have him a real torrid time.

"In the second half today David he was targeted a bit. Not necessarily physically but there were a lot of challenges that should have been free-kicks but the referee decided to play on."

Having provided the pass for Wayne Rooney's 12th-minute opener, Ashley Young was also claiming the winner, which was actually deflected past Ben Foster by Steven Reid.

It was cruel luck on Roy Hodgson's men, who were worthy of a point.

However, the dismay of the Baggies chief was matched by his incredulity at a bid for Peter Odemwingie lodged by Wigan that it has been suggested is no more than £1.5million.

Considering West Brom paid double that sum for the striker 12 months ago, since when he has scored 15 Premier League goals, Hodgson was mystified at how Wigan could come to any conclusion other than it being rejected, which it duly has.

"Peter is not for sale," said Hodgson.

"If you had seen the size of the bid, you would probably have been laughing all the way out of here.

"I don't understand teams to put in bids which are so obviously ludicrously far away from what the player's value is.

"I suppose I could put in a bid for Wayne Rooney. Alex would laugh that out of existence just as we laughed their bid out of existence."