Ferguson told reporters: "It was a good Cup tie. It ended up a really good Cup tie when they got the goal and had a really good go at it.
"When they got the goal, they then got the ball in the box. We withstood that and I think when you analyse it, we played some great football and should have scored a lot of goals tonight.
"We missed some chances but there were shots saved and I'm really satisfied with the quality of the game."
United will face holders Chelsea in the quarter-finals of the competition, if the Blues can overcome Middlesbrough in their fifth-round clash on February 27.