Paul Lambert revealed on Friday morning both James Vaughan and Korey Smith will be out of action 'for months'.

Striker Vaughan underwent knee surgery earlier this week and faces a lengthy lay off after limping out of Monday's Premier League win against Sunderland. Young midfielder Smith has also undergone surgery on an ankle injury suffered in the recent reserves' outing at Newcastle. Smith watched City's 2-1 win at Carrow Road over the Black Cats on crutches.

The duo join longer term absentees Elliott Ward (knee) and Dani Ayala (knee) on the sidelines. Zak Whitbread returned to training this week but will not be considered for Saturday's league trip to Man United.

Lambert admitted Vaughan's latest injury setback was a cruel blow for the 23-year-old striker who has yet to start a first team Norwich game.

'He is going to be out for a considerable time which is a blow because I thought he was looking really good,' he said. 'It's a pity for himself because he has battled really hard to get back but he is going to be out for a few months. I think its his meniscus which has been damaged, its a fresh injury, and we think it will take three or four months.

'Since he has arrived at the football club he seems to have had bad luck with injuries. At (Crystal) Palace he never seemed to get injured. That is football at times - you need a lot of luck at times. The operation went went and now its about his rehab. It is just one of those things. For him to be out for that length of time has shattered him a wee bit - but hopefully he'll be okay.'

Smith had yet to feature in the Premier League this season but did play in the Carling Cup defeat to MK Dons.

'Korey has done his ankle and will be out for a bit. He did it in the reserve game the other week,' said Lambert. 'He'll be out for a few months. He had to have an operation.'

Lambert insists his men are undaunted by a pending trip to Old Trafford.

'It is probably the hardest game you will get, but we have earned the right to play them, and if you dont like playing a game like this, then there is something wrong,' he said. 'I won't need to lift them because the atmosphere and the players they are going to be against will do that for them. We will give it a right good go and there have been better teams than us who have gone there and got right turned over, which shows you the magnitude of what we have to face.

'Sometimes upsets can happen and we will try everything we can to win. It is only great if you are not getting stuffed, I hear all the time it is a great day out, but it is only great if you are doing arlright, not if you are getting smacked six or seven nothing. I dont buy into it is a lovely day out for the supporters. It is only if you are giving a right good go at it.'