Wilf, Navas, Savic ? I don't think Delph is a poor player, maybe he's just not technical for Pep's midfield, I however believe Pep can get something out of Delph- perhaps convert him to a full back.
You could type names for an hour straight into this forum before you got to the three names you mentioned, Navas is a decent enough player that doesn't deserve to be bracketed into any worst ever City player category.
Savic was destroyed by the boo boys and left City and has hardly disgraced himself as a centre half, Bony was a bad buy a bad fit for a team playing the way we do.
Lee Peacock is my ultimate bad buy, shudders at the thought.
Take a read below to refresh your memory of some truly horrendous players, no doubt somebody will have said Navas in there but it really isn't true.
http://forums.bluemoon-mcfc.co.uk/threads/worst-city-players-you-remember.203634/