Alex Ferguson has claimed Jonny Evans is ``guaranteed'' a Manchester United first-team berth at some point in the future.

The Northern Ireland international stepped in for Nemanja Vidic at Chelsea a week ago when the Serbian was suspended.

He rewarded Ferguson with a towering performance at Stamford Bridge, proving the United boss dead right in his decision not to let Evans join Sunderland on loan for a third successive season.

Evans will have to be patient. Vidic returned to duties against Aalborg four days later and kept his place at Blackburn this weekend.

However, Ferguson has assured the 20-year-old he is the long-term successor to Rio Ferdinand and expects the Belfast-born youngster to eventually take a stranglehold on a central defensive place.

``Evans' career is absolutely guaranteed,'' said Ferguson.

``He is 20, Rio Ferdinand is 30 and Nemanja Vidic is 27 so, in a few years' time, he will be the first choice centre-half there is no question about that.''

Evans remains a doubt for Northern Ireland's World Cup qualifier with Slovenia on Saturday.

The defender has been suffering from a virus so severe he made the journey alone to ensure he did not infect any of his team-mates.