Phillips admitted the Wales squad had been locked in the gym during the summer following their 55-3 defeat at the hands of the All Blacks in June.
And now, he reckons, Wales are in the best shape of their lives as they bid for a place in the semi-final.
"After the game in New Zealand in June we realised the be all and end all was that we simply had to power up or we just wouldn't be able to match these kinds of teams," said Phillips.
"A lot of work has gone into the squad, especially over the last three months in terms of conditioning and understanding where exactly we are but key to the work was strength and power.
"It gives you a lot of confidence when you know you're getting fitter and faster and the performance against the All Blacks came out of hard work not luck.
"Last weekend gave everyone a boost about what we're trying to do because you know when you play the All Blacks they show no mercy.
"You can be cruelly exposed, as we were in Hamilton, and the back three did cause us a few problems but it was great to see a Welsh pack front-up to their forwards."
The message was obviously heard by Clive Woodward who revealed there was a "fear factor" within the England camp after watching Wales' performance against All Blacks.
"Seeing Wales play so well and go so close certainly makes things interesting for Sunday," he said.
"It also put a bit of fear in the camp which is usually a good thing to have within the squad before such a big game."