Man Utd boss Ferguson: Ronaldo desperate to face Chelsea
"Cristiano is nibbling in my ear all the time. He is bursting to play," said Ferguson.
"When he really is buzzing, he attacks people with such speed they are forced to go back.
"The boy was on fire on Wednesday. He was revved up to do really well.
"When you think he has had an operation, has been in rehab for two months and had not played since May 21. It was a big ask for him.
"But you have to say his performance level was outstanding.
"He has trained very well and is a natural athlete, so I have no qualms on that score. I just have to decide whether it is the right time."