Usually, when a manager's sacked, his former players will go all out to impress the new man in charge during their next game.
It's not always the immediate fixture, as the sacked coach's successor isn't always in place.
Indeed, there is already tension among Chelsea supporters - many feel Mourinho should not have been dismissed and that the Portuguese coach was thrown under a bus by his players.
If those players were suddenly to play like the Premier League winners of yesteryear, their performance might not be greeted with cheers by the home crowd - but rather boos, as it will become all-too-clear that they were sandbagging under Mourinho.
That puts Sunderland in a winning position. Their utmost need for points will guarantee a determined display, especially with Sam Allardyce in charge.
While the Chelsea players will be torn between their Mourinho conundrum and the need to impress his successor, the Black Cats will be in the perfect position to capitalise on that uncertainty.
And, even with Mourinho on song at Chelsea, Sunderland have still managed to come away from the Bridge with a win...