"The important part of being a successful team is to avoid complacency. It is a disease that has to be guarded against."
So explained Alex Ferguson when discussing the secrets of his two decades of glory at Old Trafford.
"If we were winning at half-time, that was brought up — avoid it, it is a disease. If you lose a goal, you lose the game — keep your foot on the pedal.
"With complacency, you do not see it happening, you do not see where it is coming from. But, when it hits you, you cannot get out of it, you can’t eradicate it."
Erik ten Hag would do well to listen to those sage words.
Manchester United's late collapse against Sevilla in a match they were utterly coasting in was a stark reminder of how far the team still needs to come to be anything like the ruthless winning machine Ferguson built and maintained at Old Trafford for so long.