Sounders' supporters are gaining a profile across the world and were again outstanding for the United match.
Ferguson said: "It was brilliant. The pleasing thing for me was the number of fans all mixed together.
"That was like the old days of England and Scotland, when fans could mix together and no trouble. I don't know if we could ever get back to that, but it was a pleasure to watch that tonight. The atmosphere was always good. The Sounders' support is fantastic. It's a plus-point that, it's a big plus-point, to see fans mingling together and enjoying it."