I think there's a shout for yesterday being the worst defeat in the Prem.
The rivalry - the biggest in the league
The way the game unfolded - not just a late show to do a cosmetic job on the scoreline, or skewed by a red card. 5-0 flattered us, not them
The quality of our squad - whatever limitations we have, we're not like some team recently promoted, facing the big boys for the first time
Away team won - getting battered in front of your own fans is particularly gruesome
I can't immediately think of a worse performance off the top of my head, either from United or anyone else in the league.