Eddie Jones conceded England may have been suffering a hangover from their stunning Rugby World Cup triumph over New Zealand as they slumped to a lacklustre defeat in the final.
South Africa were underdogs in Yokohama on Saturday but emerged as dominant 32-12 winners against an England side who had comfortably seen off the All Blacks in the semi-final.
Wales coach Warren Gatland, whose team were beaten 19-16 by the Springboks in their last-four meeting, had sounded a warning to England when he suggested they may have peaked too soon in that win over the reigning champions.
And Jones was not able to dismiss that notion as he gathered his thoughts after a chastening loss in Japan.
"That could be a factor, I'm not sure," he said. "I don't know why we didn't play well and this is one of those things that happens in high-level rugby.
"We thought our preparation was good, but at the end of the day it wasn't, because we didn't play well.
"You can have the most investigative debrief of your game and you still don't know what was wrong.
"It's not a good day for it to happen, we're going to be kicking stones now for four years and it's hard to kick stones for four years, so we're massively disappointed, but at the same time I've got great admiration for what the players did.
"I can't tell you how much respect I've got for how hard they've worked, how well they've played. We came up short, but it's not because of a lack of effort."
Jones was pressed on how England's efforts at the tournament should be remembered and, while he admitted they had come up short of their ultimate goal, he was looking forward to drowning his sorrows with his players over the coming days.
"We are the second best team in the world," he said. "We didn't meet our goal, our goal was to be the best team in the world, but we are the second best team in the world, so I think that's how we should be remembered.
"The only thing we are worried about now is having a few beers and after we've had a few beers today, we'll probably have a few more tomorrow and then probably Monday and then probably we'll have to pull up stumps."