The openside flanker debuted as a 20-year-old against Ireland in 2001 and is now one of the greatest players to have worn the Silver Fern.
Dagg played a blinder against South Africa in the All Blacks' 18-5 loss to the Springboks in Port Elizabeth last month in only his third match back from a serious quadriceps injury, and is more than knocking down the selection door. There are plenty of armchair selectors who have been banging on it for Dagg, too.
He bagged a double in the tournament opener against Tonga and threw a sharp offload to send Richard Kahui on his way for another five-pointer.
All Blacks coach Graham Henry said Muliaina, who he referred to as "the old bull", was under pressure from Dagg, but believed the veteran deserved a chance to show his wares.
"You've got the old bull and the young bull ... but if you don't give the old bull a chance, the old bull is not going to be able to show what he can do, and he's showed this country for the last 98 test matches what he can do," Henry said.
"He's often been the No1 fullback in the game, so we've just got to get the balance right so both have the opportunity to show they're good enough."
The depth in the squad was healthy, Henry said.
"It's still a contest. We've got a gentleman who's played 98 test matches, who's played some fabulous rugby for the All Blacks over a long period of time, playing against a young guy who could be a very, very good player. It's a contest and that's great for that particular position."
Henry hinted that he could squeeze Dagg and Muliaina into the starting XV with the Hawke's Bay rookie on the wing, but said he thought fullback was Dagg's best position.
Muliaina is one of five changes to the backline to meet Japan, alongside centre Conrad Smith, halfback Andy Ellis and wing Cory Jane.
Henry named his side yesterday but had to scratch Dan Carter, who has succumbed to a back injury and will be replaced by the inexperienced Colin Slade.
Halfback Jimmy Cowan has been elevated to the bench and Piri Weepu will cover first-five.
Adam Thomson will play at No8 in place of Victor Vito, while rake Keven Mealamu comes in and Sam Whitelock will start at lock ahead of Ali Williams.
Japan have rung 10 changes from the side that lost 47-21 to Japan in their opening game during the weekend.
Blossoms coach John Kirwan has installed former Chiefs playmaker Murray Wilson at No 10, in place of fellow Kiwi James Arlidge, who impressed in the defeat to Japan.APNZ