The Blues take on United in their first Premier League game since promotion from the Championship, and McLeish will be looking to upset the odds at Old Trafford.
United will have to regain their league trophy without Portuguese star Ronaldo after his big-money move to Real Madrid, but the Blues boss doesn't believe it will be too much of a problem.
He told Sky Sports News: "I think they have struggled for a while to find their feet, but having beaten Valencia 2-0 the other night - I wish I had Sir Alex Ferguson's problems.
"People like Wayne Rooney will adapt to the system, they will flourish, I am sure that they will flourish.
"Michael Owen looks as though he has got a good pre-season behind him and they have so many other fantastic players."
McLeish may hand league debuts to a number of new signings at Old Trafford after a busy summer in the transfer marker.
The likes of Christian Benitez, Barry Ferguson and Lee Bowyer could all line-up against the Red Devils next Sunday.