England scrum-half Ben Youngs admitted their first-half performance had been unacceptable as they went down 36-13 to New Zealand in Hamilton.
The All Blacks raced into a 29-6 lead at the break, and although England were significantly better in the second half, there was no way back from such a deficit and New Zealand wrapped up a 3-0 series whitewash.
"We let ourselves down and left ourselves with a mountain to climb," Youngs told Sky Sports. "Against New Zealand you can't leave yourself with such a huge chase and we paid the price."
Asked what went wrong, Youngs added: "I really don't know, we'll have to have a look at it. We pride ourselves on defence and spend a lot of time on it but the first half wasn't good enough. Whether it was individual mistakes or collectively we'll have to have a look but you can't give them that big a lead and expect to be in the game."
Harsh words - "probably unbroadcastable", according to Youngs - were exchanged at half-time before England came out much improved.
"They were honest words, this is an honest group," he added.
"The second half things came off a little bit more but the damage was done. We put in great performances before this but you'll remember how we did in the last game... Unfortunately today puts a dampener on what we did in the first games.
"It's just tough lessons against these boys. This is a young squad with a World Cup coming up and it's about getting more and more experience.
"Unfortunately you have to go through these games to get experience."
England head coach Stuart Lancaster admitted his own frustration at the Jekyll and Hyde performance but said it was important not to forget the positives on show.
"We were hugely disappointing in the first half," he said. "It's a high-quality All Blacks side but the first half was poor from us. I thought we showed tremendous character to come back in the second half and we created some great opportunities but unfortunately we didn't take them and we were beaten by the better side."
While making no excuses for the opening period, Lancaster believes the second half gives England a platform to build on going forward.
"I'll say I'm proud of the second-half performance and as an England team that's what we need to deliver," he said.
"There's a lot of be proud of and positive about because it was a young side out there.
"We want to be the best in the world and to do that you need to be there for 80 minutes, not 40 or 60. We're a long way towards that and in games like this you find out a lot about your players so I'm not going to emotionally overreact to one game."