The Black Cats tumbled into the Championship last season as Moyes stuck rigidly to tactics that were not working, spoke with intense pessimism and - perhaps most frustratingly - relied heavily on players he knew well but that were not of the required quality.
And it looked as though West Ham should have heeded that warning after the opening weeks of his reign, the rot continuing at speed.
But something has changed in recent weeks and the Hammers followed up a heartening tight defeat at Manchester City with consecutive clean sheets and four points from home clashes with Chelsea and Arsenal.
Moyes has altered his side, got key men playing and crucially changed his goalkeeper - deciding Joe Hart's dismal showings did not warrant a first-team place.
Adrian has looked like a serious improvement since coming into the team and now looks to be established as the first choice heading into a key festive spell.
Not only has Moyes' call paid off but he has also shown himself capable of making a big decision, dropping the England number one - a much-heralded summer signing - for Adrian who had looked to be on his way out of the club.
If West Ham are to continue their climb away from the Premier League's bottom three, there could well be more tough decisions.
It is up to Moyes to act as ruthlessly and swiftly as he did with Hart in order to maintain hope at London Stadium.