The seasoned campaigners have formed the central defensive partnership for the past five games since Phil Jones played alongside Vidic in the Community Shield against Wigan Athletic at Wembley.
Although Jones and Rafael are both close to being available for selection again after injury to provide more defensive options, the boss feels he has made the right call in choosing his most experienced central pairing despite being asked whether it was a fitness risk considering Vidic is 31 and Ferdinand is 34.
"It is something which I'm aware of," admitted Moyes. "I'm sure nature will take its own course in time but I'm quite comfortable with Jonny Evans, Chris Smalling and Phil Jones.
"I just felt at the moment that I've taken over a new job and it was important I got a little bit of rhythm. I don't like the word 'rotate', but I will change players at different times.
"I just felt, at the moment, because of the start to the Premier League that we had, my mind was made up that I was going to keep it quite strong in the opening period of it and then see what happens after that.
"Their fitness has been great, the two of them. They felt really good through pre-season and I think they're both enjoying it."