The 50-year-old Scot has agreed to replace his compatriot in the Old Trafford hot-seat and the former Everton manager is set to sign a six-year deal with the 20-time English champions.
Ferguson led United to their 13th Premier League crown last season and Moyes, who is set to officially take charge on 1 July, is tasked with retaining the top-flight crown.
And Villas-Boas reckons the Red Devils’ “aura of invincibility” could disappear if Ferguson’s successor takes time to settle into his new role.
“The aura that Sir Alex had, David Moyes does not yet have,” the Times quotes Villas-Boas as saying.
“This could have a direct influence on the players of Manchester and their opponents.
“United had, because of Sir Alex’s history of winning, an aura of invincibility. The fear made everything harder and may continue if [Moyes’s] adaptation is fast.
“The structure and squad are top, but there was one voice. I am curious to see [what will happen].”
Get enhanced odds of 5/1 on Sevilla to win the Europa League on Wednesday with Paddy Power.