England defence coach Mike Ford says the players' mental approach will be the key to success in Saturday's Six Nations clash with Wales.
Ford has had limited chances to make his point in training this week
"You need to build an edge in training, and the challenge is that we've not really trained this week," he said.
"We'll know in the first five minutes if the edge is there or not. My concern would be what are we going to do if it doesn't go right early on?
"Are we going to succumb like we did in Ireland, or have we learnt our lesson?"
After defeating France at Twickenham on Sunday, England allowed their players to recover before resuming training at their University of Bath base on Wednesday.
England will also have a light session at the Millennium Stadium on Friday before the match on Saturday.
Ford said there had been several flare-ups between England team-mates in the intense build-up to the France game, and joked that time had been too short for any altercations this week.
"We've had one training session and there's no time for fighting!" he said.
"I told them that if they wanted a fight, to go and see (former England hooker and now Academy coach) Dorian West!"
Ford said England had made major strides forward in their defence against France after suffering a record 43-13 defeat by Ireland in their previous outing.
And the former Saracens coach said England would need to show the same fortitude against Wales' expansive style.
You've got to look at the win over France as England's best performance since the last World Cup
England defence coach Mike Ford
"If Wales have a purple patch and get three points and then get good field position and start throwing the ball around, what are going to do?" he said.
"We need to stand up and be counted and not die like we did in Dublin."
Ford, who has appointed blind-side flanker Joe Worsley as "defence captain" for the Wales match in place of the injured Mike Tindall, said he had been hugely impressed by England's performance against France.
"I think you've got to look at it as the best performance since the last World Cup," said Ford.
"I don't buy into that theory that France played badly at all. For someone like me who analyses the teams, I can say they've played like that all the way through.
"It's the first time we've beaten France since the 2003 semi-final, and given the circumstances and the changes we had it was an excellent performance.
"You've got to give credit to Brian Ashton for making the changes and to the players for the courage they showed in the way they performed."