England were in front and, in McClaren's eyes, in control when Cantalejo ruled Wayne Rooney tugged Konstantin Zyryanov's shirt inside the box.
The foul was clear enough, but TV replays showed the foul occurred outside the area. Yet up stepped Roman Pavlyuchenko to level from the spot - and when the Russian substitute netted again four minutes later, England's dreams were in tatters.
McClaren now knows if Russia beat Israel in Tel Aviv next month then Guus Hiddink's men will qualify at the expense of his own side once they have completed the formality of beating Andorra in Moscow four days later - on the same night England are completing their campaign against Croatia.
Such a scenario would see England miss the final stages of a major championship for the first time since the 1994 World Cup, cost the Football Association millions in lost potential sponsorship - and almost certainly McClaren his job.
For that depressing situation, McClaren feels Cantalejo should shoulder responsibility.
"It is an absolute disgrace," fumed McClaren.
"We were comfortable, and they were running out of ideas. If that penalty had not been awarded, I am absolutely confident we would have won the game. We were in total control.
"I am not blaming anybody - but the penalty was given by a referee in a bad position because it was outside the box.
"Because of one decision, we went from being in a winning position to losing."
McClaren did not mention, however, the fact that the officials also failed to spot that Rooney was marginally offside when he sent his first-half opener arrowing into the roof of Russia's goal.
Cantalejo could hardly be blamed for Steven Gerrard's awful miss at the start of the second half - when a cooler head from the captain would have seen England establish a two-goal lead and pave the path to next summer's finals in Austria and Switzerland.
Instead, McClaren is left pinning his hopes on Israel - who did hold Russia to a draw in Moscow earlier in qualifying, although that was at a time when they had some hope of reaching the finals themselves.
"Nobody likes losing games, and I certainly don't," he said.
"The players are devastated in the dressing room - but we stick together.
"This group is not over yet. It is out of our hands - but it is not over."
Understandably, McClaren refused to get into any discussion over his future - or the outcome in Tel Aviv next month, given the two situations are inextricably linked.
"It was in our hands - now it is not," he admitted.
"But Russia still have to go to Israel and win. The pressure is still on them. We just have to wait.
"As I have said all along, this group is decided over 12 games - not 10 or 11. Let's see where we end up."