But perhaps in a strange way, the 1-0 win over Southampton on Saturday will be the performance that makes their rivals worry most.
It kept them level on points with Manchester City at the top of the Premier League and, while they may be behind on goal difference, a free scoring side isn’t something you necessarily associate from José Mourinho.
The victory over Southampton was as trademark Mourinho as it gets; a well-organised, strong defensive display accompanied with an admirable execution of a game plan.
He even threw in some touchline controversy after being sent off for going on the pitch, although that was harsh.
He had been trying to reorganise his team as Southampton mounted an attack and briefly stepped over the touchline.
When asked after the match why he had been dismissed, Mourinho said: “I don't know. You have to ask the referee.”
He’s escaped a ban for that though – which is probably a fair enough outcome. But Mourinho is working his magic once again.
His Chelsea team of 2004/05 holds the record for fewest goals conceded in a season with just 15.
We are only six games in, but the Red Devils have conceded just two league goals this season.
It's too small a sample to draw any conclusions from, but if their form carries on like this they will concede less than that 15.
Under the Portuguese, Chelsea were known for their 1-0 and 2-0 wins and Manchester United’s performance at Southampton was classic Mourinho from his first spell at Stamford Bridge.
Even with his team not at their best, and with only 39 per cent possession, they held strong at the back and got their reward when Romelu Lukaku scored in the sixth successive game for club and country.
Mourinho admitted after the game it was the first time his team had been tested like that: “The way we attack is something we are doing since the start of the season, to defend like that was the first time that had happened to us this season.”
But he now knows his side can do that and, perhaps even more than the big wins from earlier in the season, it send out a warning to his title rivals: that Mourinho has built a team in his image.
He won a domestic title in his second season at Chelsea during both spells, and at Real Madrid, as well as at Porto and Inter Milan, where he also delivered the Champions League.
The signs are United could very well repeat the feat at Old Trafford.