Why that moment of madness will haunt Terry forever
As he walked towards the tunnel, his face reddening, he must have thought he had cost his team a place in the Champions League Final.
In the end, John Terry only cost himself.
He cost himself the honour of being part of one of the most incredible team performances in Champions League history.
He cost himself the chance of being involved in one of the most remarkable feats of defiance football has ever seen.
He cost himself a part in Chelsea's momentous draw with Barcelona. Against all odds. Against astonishing odds.
He cost himself the privilege of being part of an occasion that somehow matched the 1999 Champions League final here for mind-blowing drama.
And, yes, he cost himself the chance for the shot at redemption he has dreamed of ever since he missed that penalty in the shoot-out in the 2008 final in Moscow.
The brutal reality comes down to this: Chelsea will play against Bayern Munich or Real Madrid in the final at the Allianz Arena later this month but their captain will not.
His 37th minute red card for kneeing Alexis Sanchez in the back has seen to that.
Somebody else will lead Chelsea out in Munich now. And if, somehow, with four of their first choice players suspended, Chelsea win, someone else will lift the trophy.
Not Terry, not the man who believes he is destined to lead and destined to complete Chelsea's epic quest for club football's holy grail.
He will be in the stand somewhere in a suit and tie, watching as another man lifts the trophy that he always believed fate would hand to him.
It is hard to fathom exactly why the Chelsea skipper did what he did last night.
The moment froze the blood just like David Beckham's flick-kick at Diego Simeone in 1998 and Wayne Rooney's stamp on Ricardo Carvalho in 2006.
It is hard to guess why he snapped and kneed Sanchez hard off the ball.
It is hard to imagine why it was then, not even half way through one of the most important matches of his career, that madness enveloped him.
It is so baffling, so inexplicable, because Terry has charted his way through the chaos buffeting his career this season with a strange stoicism.
Hurl controversy or derision or disgust towards him and he has sailed on unabashed and apparently untroubled.
He has been accused of racially abusing Anton Ferdinand and he has lost the England captaincy and yet still he has refused to fold.
More pertinently, he has never bowed to provocation on the pitch. When he has been baited by opponents or ridiculed by fans, he has refused to react.
He has kept his head when others would have surrendered to angst or anger or wounded pride.
But here, suddenly and catastrophically, something finally broke inside him.
Maybe it was because Chelsea had just gone a goal down at the Nou Camp and their defence had finally been breached after 127 minutes of heroic resistance against the best footballing side in the world.
Maybe it was because in that instant, he thought he had sensed his last hope of winning the Champions League fading to dust.
Do not forget that this is a man who has never been able to watch a replay of the 2008 Champions League final in Moscow.
A man who has never been able to bring himself to see the images of the penalty shoot-out at the end of extra time.
A captain who knows he could not bear to see a replay of the moment he missed the kick that would have won the Champions League for Chelsea.
His fear must be that, despite everything he has won, despite everything he has given to the club, that moment will taint his career.
So maybe when Sergio Busquets brought the scores level on aggregate for Barcelona, it was finally too much for Terry.
All the old images of Chelsea's cursed love affair with this competition must have come flooding back.
The so-called ghost goal against Liverpool at Anfield in 2005 that effectively knocked Chelsea out.
The shoot-out in Moscow, Didier Drogba's bulging eyes as he confronted the referee at the end of the injury-time loss to Barcelona in 2009.
Winning the Champions League, after all, is the measure of modern greatness for a footballer.
His England teammates, Rooney, Rio Ferdinand and Paul Scholes have won it. He has not.
For a strong man, it is an area of vulnerability.
For someone who sometimes seems physically indestructible, it is an Achilles heel.
So even though there was still so much time left last night when he did what he did, maybe going behind was enough to trigger Terry's fall.
Maybe it was enough to make him run up behind Sanchez and jab his knee hard into his lower back on the edge of the Chelsea box.
Perhaps he thought he would get away with it, that the Turkish referee would not see what he did.
But the referee's assistant saw it and pointed it out. Terry pretended to be astonished but deep inside, he must have known he was in trouble.
His consolation is that he did not cost his teammates a place in the final although their resistance was so desperate that another three earned suspensions.
It will be scant comfort, though, for a man who just earned himself another moment that will haunt him for the rest of his days.