The Ecuador winger struck in this week's Champions League win over Bayer Leverkusen.
"Youâ€™ve got Antonio Valencia back to his best," said Ferguson.
â€œHe has changed the number of his jersey again â€“ itâ€™s amazing how that can affect a player. Maybe it was a great thing for him to do that. He used his initiative to go back to 25 [from No 7] and he was fantastic."