The Portuguese winger replaced the injured Phil Jones late in the first half before scoring and providing an assist for Chicharito in Monday night's 2-1 FA Cup win over Reading and Ferguson was thrilled with his performance after some mediocre form of late.
"He's got great talent, we know that," said Ferguson.
"I had a feeling he would win the game for us. You could see he was right on form the moment he came on.
"He had two great strikes immediately and was a threat to them the whole night.
"It's a good addition. If he keeps that form it makes my job more difficult now."