Vidic confirmed yesterday his intention to seek a fresh challenge when his contract expires at the end of the season. With Rio Ferdinand also virtually certain to be leaving Old Trafford, it means Moyes must plan for life without the two men who have been the cornerstone of the United defence for almost a decade.
Numerous big names are expected to be linked with a summer transfer to the club, but in Jonny Evans, Phil Jones and Chris Smalling, Moyes already has players with a combined total of 384 United appearances to call upon. Among them, the trio have also accumulated 49 international caps and six league titles.
The United manager said: "People who know football will tell you centre-half is probably the toughest position. I even think it is harder to play centre-half than goalkeeper now.
"The movement and quality of the centre forwards means it is very difficult to play a young centre-half. Phil Jones, Chris Smalling, Jonny Evans are already here. We will give them an opportunity to show what they are capable of."
In addition to a new anchor at the heart of his defence, Vidic's impending exit means Moyes is also in search of a new captain. Darren Fletcher and Michael Carrick offer the Scot options, but the obvious choice - if he signs a contract extension - would be Wayne Rooney.
"Captain of this club is a really big job," added Moyes. "It holds a massive responsibility. You have to be respected by your players and realise what the club stands for."
The former Everton manager revealed it was a mutual decision to sever ties with Vidic after over eight years' service.
"When I arrived at the club and saw Vida up close I thought 'wow',"he explained. "He is a fantastic defender and a great warrior.
"He still plays a big part here but we felt it was the right thing to be open with it. His contract was coming to an end. We felt it was the right thing for him and we decided it was the right time to do it for the club."
With Evans not recovered from the calf injury he sustained in last Saturday's defeat at Stoke, Vidic will return from a three-match suspension in tomorrow's Premier League encounter with an ailing Fulham outfit, who are managed by Sir Alex Ferguson's former United assistant Rene Meulensteen.
Marouane Fellaini will not be available, though, after suffering a minor groin strain in training. Meanwhile, United will embark on some warm-weather training immediately after their trip to face Arsenal at the Emirates Stadium in midweek.