The former Everton boss has taken the reins from Sir Alex Ferguson, who retired at the end of last season after 26 years in charge, and Villas-Boas believes that the club have lost their air of invincibility.
"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]."
Moyes signed a six-year contract when he was named as Ferguson's successor.