"What cost us in the end was an inability to start at the same pace and tempo they did," said Johnson.
"You can't replicate the tempo and physicality of Test rugby in training, much as we'd like to. We were rusty in all areas early on and that is going to hurt you - 14-0 is not a great place to be.
"To get back from that position and give ourselves a good shot was good but it comes down to scoring when you get the opportunities."
After trailing 20-6 at half-time, Johnson's troops were much more competitive after the restart.
A Dylan Hartley try - the first five-pointer the All Blacks have conceded on their European travels since the 2007 World Cup - and a Toby Flood penalty buoyed the home fans but when Dan Carter knocked over two penalties, taking the fly-half's match points tally to 16, New Zealand were home and dry.
Just like their opening Test defeat to the Wallabies on 12 June in Perth, Johnson was left to reflect on what might have been.
"We created more opportunities than we had done in the last two games combined against this team," continued Johnson.
"They haven't conceded a try in Europe for a couple of years. We probably should have scored another one."
Indeed, the tourists were lucky to escape when Ben Foden was held up over the line at the end of the first half and even more forturnate when Shontayne Hape spilled the ball under Isaia Toeava's last-ditch challenge as he stretched for the line in a pulsating climax.
But while Johnson rued his side's profligacy, All Blacks coach Graham Henry was delighted with his side's mean defence as they bounced back from last Saturday's 26-24 loss to Australia in Hong Kong.
The players were frustrated afterwards and that is good
"It's always a hard battle at Twickenham," he said. "Every time we play here it's a hard slog. They're a good side.
"There are bits and pieces we can improve on but the bottom line is we had a good win."
Henry's captain Richie McCaw, though, accused his team of slackening off in the latter stages.
"We're our own worst enemy at times," he said. "A couple of times we had space and just gave the ball back to them and ended up under pressure because of it. Leading into the last 20 minutes we just kept giving them opportunities."
Johnson, meanwhile, drew solace from his players' post-match despondency ahead of their next Test against Australia next Saturday.
"The players were frustrated afterwards and that is good," opined Johnson. "I would be disappointed if they were all pleased with their comeback. They know they have got to be better than that."
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