The genial Welshman, cruelly denied a Lions Test berth against South Africa last summer by injury, knows he must produce a trademark performance if a 43-year losing streak against the All Blacks is to be ended.
Pressure on his broad shoulders is enormous, yet the Cardiff player believes he has already done the hard part - being selected above his great friend and rival, Pontypridd's Paul John.
Kevin Bowring, the Welsh coach, gave John the No 9 jersey against Tonga last week, but when Howley went on in the second half, he single-handedly transformed the side.
"I knew that I would need to hit a certain standard if I wanted any chance of playing against New Zealand," Howley said.
"Paul and myself have been challenging for the scrum-half spot over several years, and that rivalry will continue. The more competition there is for your place, then the better player it makes you.
"I was pleased with my Test comeback, but playing 20 minutes against Tonga will be nothing like opposing New Zealand. I will be pitting myself against the world's best scrum-half [Justin Marshall], while the team must compete with the All Blacks, producing awesome rugby."
Howley rebuffs any suggestion that Wales will resort to a tight set-piece game, the popular theory which many believe has credence, given how effectively the English Rugby Partnership XV took on New Zealand in midweek.
"It has been said that if you risk playing the high-tempo game against New Zealand, you will be blown apart," Howley said. "Wales are developing a game the players are comfortable with - one played at considerable pace, so this is the acid test."
Wales will be in exile for the next 18 months, while work continues on the pounds 120m Millennium Stadium, but Wembley has proved popular with their fans - tomorrow's attendance will be 78,000.
Niall Hogan, the 26-year-old London Irish scrum-half, will deputise for the injured Brian O'Meara on Ireland's replacements' bench for Sunday's Test against Canada in Dublin.Reuse content