Casemiro had been the outstanding performer of a game that appeared to have been snatched away from his Manchester United team. A smooth and commanding presence at the back of the midfield, he provided the platform for the visitors to dominate the first half.
And when Chelsea rocked them with a late Jorginho penalty after a lengthy period of second-half drift, it was Casemiro who refused to accept it would be one of those hard luck stories. David de Gea had not been required to make a save for United before he fished the penalty out of his net.
The clock showed that we had entered the fourth of six additional minutes when Luke Shaw hung up a cross from the left and Casemiro made his leap, soaring above Ben Chilwell and straining every sinew to head back towards the far corner.
Kepa Arrizabalaga, who was impressive again, stretched out a hand and he managed to paw the ball onto the inside of his post and there, as it bobbled along the line, time seemed to freeze. The Chelsea goalkeeper clawed to safety but did it cross the line? A buzz on the watch of the referee, Stuart Attwell, confirmed that it had - by a matter of millimeters - and United could celebrate raucously in front of their fans.
Those who had travelled had spent much of the previous three days questioning what had gone through the mind of Cristiano Ronaldo. His flounce off towards the end of United’s impressive home win over Tottenham on Wednesday night and the subsequent in-house suspension cast long shadows. Now they could ask the same thing of Scott McTominay.
On as an 80th minute substitute, the midfielder who has been a foul or yellow card waiting to happen for much of the season draped his arms around another replacement, Armando Broja, as a Chelsea corner came across. It was a highly risky move and one that practically invited Broja to go to ground, which he did. Attwell had to give the penalty and Jorginho converted with a skip and ice in his veins.
It looked set to be the latest triumph for Graham Potter and perhaps the most significant of his eight-game Chelsea tenure. The manager had set up in a 3-4-2-1 system only to ditch it after 36 minutes as United overwhelmed his team in midfield. It was a brave move to hook the unfortunate Marc Cucurella and introduce Mateo Kovacic in a rejigged 4-4-2 diamond but Potter did not sit on his hands. He acted and his team were able to dig out a foothold.
Kovacic made a difference and Chelsea were better, although they continued to lack cutting edge in the final third. It was a game when Raheem Sterling and Pierre-Emerick Aubameyang could get nothing going.
The penalty threatened to change everything because Chelsea had entered on a run of five consecutive clean sheets. One more and they would have a statement victory. Enter Casemiro, the £51m summer signing from Real Madrid, and how he enjoyed the moment after his first goal in United colours. Chelsea remain unbeaten under Potter.
United had settled straight away, knitting together some nice sequences, Casemiro prominent, so too Bruno Fernandes and with Raphaël Varane stepping up with the ball. Arrizabalaga was the busier goalkeeper, his first save coming after Antony had spun and unloaded from the edge of the area.
United were kicking themselves at half-time because they should have been in front. They had two big chances, the first created for Marcus Rashford in the 28th minute by a slide-rule Fernandes pass after Casemiro and the recalled Christian Eriksen had combined to rob Ruben Loftus-Cheek. Rashford’s first touch was heavy and Arrizabalaga was out to block the attempted dink.
The second followed a diving, clearing header from Lisandro Martínez and another throughball from Fernandes, this one for Antony. The winger had to curl it with his weak right foot to bring it back inside the post and he could not do so. In between times, Rashford eeked out a yard inside the box to extend Arrizabalaga.
Apart from a Mason Mount cross that Varane stretched to clear ahead of Aubameyang, Chelsea offered little before Potter’s tactical change. They hinted at something after it in the minutes leading up to the interval but twice Aubameyang could not bring the ball under control when well-placed while he also smuggled a shot past the post.
There was an ugly undercurrent, with homophobic chants from the United support and abuse from those in the home seats for Varane, whose crime was to pull up with a muscle injury. He was emotional as he left the pitch, plainly fearing for his World Cup with France.
Sterling fluffed an attempted touch for Loftus-Cheek and Trevoh Chalobah sent a header against the top of the crossbar. For United, Fernandes watched Arrizabalaga turn a shot from him around the post. Cue the late drama.