The Belgian was in an inspired mood, not only bagging a brace, but helping Chelsea back into the game with an assist for Frank Lampard, who nodded home the Blues' equalizer to cancel out Jozy Altidore's 14th-minute opener.
From that moment, the Blues took control of the game and it was Hazard who proved the difference, scoring twice before a Phil Bardsley own goal sealed a 4-3 victory.
Could Mata do enough to show Mourinho he is worthy of a regular starting place in the Chelsea team?
Of course he could, it's Juan Mata after all, but it was Hazard who stole the show with one of his finest performances of the campaign.
It's just what Mourinho and Chelsea needed, too.
The games are beginning to come thick and fast in West London and with the likes of Hazard appearing to hit form, it will make the coming weeks a far more pleasant time for the Chelsea boss.
Whereas it's been rather the contrary in recent years, it's around this stage of the season when Mourinho's Chelsea teams of the past often stepped things up a gear and asserted their authority on the Premier League.
Of the 19 games Chelsea have played in December when Mourinho has been in charge, they have won 15 and drawn just four—an impressive statistic that outlines how formidable they have been.
Gaps are beginning to appear at the top of the table right now and Mourinho knows his team is perfectly positioned for an assault on Arsenal's early-season dominance.
While Chelsea were defeating Sunderland at the Stadium of Light, Manchester United suffered another defeat at Old Trafford—losing 1-0 to Everton—leaving them 12 points behind the Gunners and eight behind Chelsea, who sit second in the table.
Even Tottenham Hotspur are looking frail in sixth position, six points behind the Blues and in desperate need of rediscovering their form.
It's why Chelsea's victory at Sunderland was such a vital one and why the performance of Hazard will be rightly applauded by his manager.
Now is the time Chelsea need to be putting an element of breathing space between them and their rivals. In the case of United and Spurs, it's mission accomplished.
Now for Arsenal and Manchester City.
If Chelsea are to do that, they need the likes of Hazard to be stepping up when it matters most. Without Oscar, who has been their best player to date in 2013-14, there would have been a few questions as to how they would adjust on Wednesday.
Hazard answered them in emphatic style.
Garry Hayes is Bleacher Report's lead Chelsea correspondent and will be following the club from a London base throughout the 2013-14 season. Follow him on Twitter here @garryhayes