The United winger impressed on his return from injury towards the end of last season but the manager feels he needs to handle the Ecuadorian with care.
Valencia missed out on a large chunk of the 2010/11 campaign following a serious ankle injury sustained against Rangers in the Champions League and was also sidelined after being hurt whilst on Copa America duty for his country in the summer.
"I had a chat with Antonio yesterday," Sir Alex revealed to MUTV after the 3-0 win in the Carling Cup. "He, himself, says he's needing games.
"He was a long time out and has been back but probably needs another few games. Tonight was another one."
Valencia certainly showed no signs of rustiness when hammering in the third goal at the EBB Stadium but, after also being used at right-back recently, the wide man will be hoping to prove his fitness for another stint in his preferred position.