The Norway striker struck three goals in the 4-2 win.
Carew said: "We were struggling in the first half and the gaffer had some serious words at the break.
"I won't go into it but you could see it on the pitch what happened. Ashley's goal was really important and it gave us a great boost and the team had a great feeling and I was sure we were going to get a second goal."
Carew is certain Villa can now cash in on the experience of having played so recently at Wembley, albeit in a 2-1 defeat by Manchester United.
He said: "We really want to get to the final again now we know what Wembley is about. It was not a great experience for us but we have a great chance to get back there."