David Moyes has warned skipper Nemanja Vidic he cannot expect to walk straight back into the Manchester United team.

Vidic is ready to return after missing two games with a minor injury suffered in the Premier League defeat by Newcastle at Old Trafford on Dec. 7. Yet those two matches have both been wins, in which United have managed to keep successive clean sheets for only second time this season.

Jonny Evans and Phil Jones looked particularly untroubled at Aston Villa on Sunday. And whilst Vidic has been the cornerstone of United's defence following his arrival from Spartak Moscow almost eight years ago, the Serbian has been plagued by injury since rupturing his cruciate ligaments in the Champions League to Basle in December 2011.

With Rio Ferdinand now 35, Moyes is known to be on the lookout for central defensive reinforcements.

Yet, even amongst his current squad, it seems Vidic will have to work to win his place back.

"Nemanja is just about ready to play now," said Moyes. "But we have five centerbacks. We can use Phil Jones, Chris Smalling, Jonny Evans, Rio Ferdinand and him. There is competition for places there and you are going to have to play well to stay in the team."

Moyes also feels he is blessed to have worked for three clubs who are not part of the hiring and firing culture. Steve Clarke and Andre Villas-Boas have both been sacked following weekend defeats and there is intense speculation over the future of Cardiff 's Malky Mackay following further friction with club owner Vincent Tan.

Yet Moyes is under no internal pressure at United, despite a difficult start to his reign, with the Scot assured of the time he needs to make a success of the job, just as he had at Preston and Everton .

"It makes me realise how lucky I have been at the clubs I have been at," said Moyes. "I worked for great people at Preston, great people at Everton and my short experience at Manchester United tells me I am working for really good people here.

"Maybe some of the other managers haven't been as fortunate as I have."