"Life is about iterations, tweaking, adapting. They are not changing anything massively. They wanted line speed and have worked on it really well."
Mitchell was Clive Woodward's England forwards coach in the late 1990s when Greenwood was playing, and the big centre revealed what the Waikato legend had brought to the party.
"He used to always say 'let the dog be the rabbit' in a slightly different tone," said Greenwood.
"It scared the living daylights out of me and certainly introduced to me what life was like in New Zealand in terms of the ferocity of your rucking. He was proper, proper tough."
Greenwood said 2018 represented a blip for England — who had top players missing at key times — after two years of unbeaten rugby.
When asked if England could maintain the intensity which has seen them upset Ireland and crush France in 2019, Greenwood said they probably didn't need to.
A third string side would beat Italy at Twickenham, and Scotland hadn't won there in 35 years. That left the clash against Wales in Cardiff next week as by far the biggest assignment remaining in this Six Nations tournament.
Greenwood is increasingly optimistic about England's World Cup chances, while predicting an off-colour Irish side would rise again.
"Oh to be the hunter and not the hunted," said Greenwood, about Ireland's Six Nations form lapse.
"The All Blacks have set the bar in terms of of retaining credibility as the number one. Ireland had the most unbelievable year in 2018 but they are having a bit of a blip, a bit of a wobble.
"England were supercharged and went out and battered them on the gain line, but Ireland will come again.
"Ireland will finish the Six Nations strong and be ready for the World Cup. They had such a big year in 2018 and it is difficult to keep going to the well. But they will be a force to be reckoned with in Japan."
Greenwood added: "I've upgraded England's status — they will be in the semifinals and who can predict after that?"
