O'Neill said: "Milner was sensational. He is a character-and-a-half and his game has reached a new level. There is no question about that.
Aston Villa rally to keep Everton to a draw"He is seeing the passes, moving into positions even though he hasn't played central midfield even 15 times yet.
"I think that is his position. He has moved his game on again. He gets into shooting positions as well.
"He said himself at the start of the season that he could score more goals but sometimes you have to be in a certain position to do that.
"If you are wide and crossing things in, it is hard obviously. His overall game from centre midfield has been fantastic."
Captain Stiliyan Petrov also highlighted the fighting spirit of the Aston Villa team by defying an Achilles problem to lead them to a first final in 10 years.
O'Neill said: "Petrov came over and said he was having a problem with his Achilles. It was a bit more than a problem because he had to get injected at half-time.
"I was delighted with his performance considering I didn't think he would see a minute after half-time at all.
"His overall performance and leadership helped us enormously in the game and I am as delighted for him as I am for anyone."
The Villa fans were less then enamoured with their side's uncertain start to the game and O'Neill believes they must be more tolerant.
He said: "The crowd have to learn to stick with the side and they cannot get frustrated.
"We have gone 2-0 down and normally speaking that might be out of sight.
"But these players are capable of fighting back - and it is better if the crowd stay with them.
"I understand their anxiety and frustration at times but you have got to stick with these players because they can play."