The former Ibrox boss believes this year's Scottish title winners have the muscle and might to stand toe to toe with United.
Big Eck told the Scottish Sun: "People remember the stunning goal by Diego Forlan in the game at Old Trafford but on the night we were wimps.
"I'd made a major decision that week that I was going to dispense with some experienced players like Nuno Capucho and Emerson. I went to Old Trafford with a rookie midfield. Mikel Arteta was still 21 and Stephen Hughes was only 20.
"We were a long way short of United in terms of quality and experience. Mikel and Stevie are both quality players but they just lacked the know-how of Keane.
"Looking at Walter's team going down there on Tuesday night, you have to say they have more power in midfield.
"We had one or two cracking individuals but, at that time, we didn't have the team ethic that Walter has instilled in Rangers again. He has them organised and he makes sure they are hard to beat.
"Walter has the great experience of working with the national team and going all the way to a European final.
"He has a great reputation in the game and even big-name guys he's worked with at Everton and United don't have a bad word to say about his prowess as a coach or as a bloke."