The Ecuadorian, who signed from Wigan Athletic in the summer, broke his scoring duck at the club in the Premier League win over Bolton on the weekend and backed it up with the winner against CSKA Moscow on Wednesday in the Champions League group stage.
Ferguson said that Valencia was now finding his feet and expected him to start stringing more consistent performances together.
"He has been the plus point for the last two weeks," the Scottish tactician said of the Ecuador international.
"He is settling into the club, his confidence is stronger and he has tremendous assets for a wee player - strength, balance, feet and a good crosser of the ball.
"The area he hadn't shown was goalscoring ability.
"We said when we signed him this was his challenge to progress as a footballer.
"Now he has scored two in two games and that will help him."