McLaren opted not to make a precautionary change of Lewis Hamilton's faulty gearbox before the Japanese Grand Prix because the outfit wanted to give him a fresh unit for the final three races.
Hamilton's chances of fighting for victory at Suzuka have been compromised by the five-place penalty he was given for needing a new gearbox prior to qualifying.
And although the issue could have been avoided had McLaren opted for a free change of Hamilton's gearbox prior to the weekend, the team said it did not want to do that because that would have meant stretching the unit until the final race of the campaign.
Gearbox reliability will be especially tested at the season finale in Abu Dhabi, with the characteristics of the Yas Marina circuit especially tough on the units.
"We could have changed it but we wanted a fresh gearbox for the last three races," McLaren team principal Martin Whitmarsh told AUTOSPORT.
"Hindsight is a wonderful thing. If you know you're going to fall off, you don't leave the garage, but you don't know those things until you have got the data.
"The gearbox, it went through the tests, it looked fine, but these things, like all parts of the power train of an F1 car, are very delicate indeed. And if they go outside their normal operation it is easy to damage them. The shame is we didn't pick it up until we had fitted it and run it in P3."
Whitmarsh said that the gearbox problem was a legacy of the collision Hamilton suffered with Mark Webber at the Singapore Grand Prix.
"There was an over-rotation of the differential and no outward signs of it," he said. "Clearly it damaged the diff which is in a sealed box, but yesterday after the end of P3 we could see that there was a big pressure rise which was probably a blocked filter, and indeed it turned out to be.
"Once you have a blocked filter you have to go in hunt of the source of that, which turned out to be a differential."