That will provoke another rethink from the All Black panel who want to take a squad of 29 players to Apia and will need to go deeper into their pool of standby players, especially backs, to fill out that group.
Dagg has suffered several setbacks this season with hamstring problems and has been out of action with the Crusaders for some time while teammate Colin Slade missed the final few games after damaging his thigh.
Piutau strained knee ligaments and while he was supposed to play in the Blues' final pool game he hurt his hamstring in a final training run and had to withdraw.
Blues skipper Jerome Kaino had surgery to repair a badly broken finger which took him out of the last five games with an optimistic forecast he would be fit for Samoa. He is reported to be tracking well and on schedule for that international.
Meanwhile Kerr-Barlow's condition will be monitored in several club rugby matches and then in games for the NZ Maori with 2011 World Cup halfback Andy Ellis ready to start against Samoa.
Tighthead prop Faumuina needs longer rest with a neck injury.
If the Hurricanes and Highlanders players are not available for the Samoan test, selectors will have to call up other backs who were not named in the original group of 41 which also had Ellis and prop Nepo Laulala on standby.
A total of 13 backs, including all three halfbacks, out of the 19 named in the squad, will miss the Samoa test if the Hurricanes meet the Highlanders.
If that occurs, the selectors will have to settle on three more back reserves and probably another couple for the extended squad travelling to the Pacific Island.
Likely team to play Samoa
15
Israel Dagg
14
Charles Piutau
13
Ryan Crotty
12
Sonny Bill Williams
11
Colin Slade
10
Daniel Carter
9
Andy Ellis
8
Kieran Read
7
Richie McCaw (c)
6
Jerome Kaino
5
Brodie Retallick
4
Sam Whitelock
3
Owen Franks
2
Keven Mealamu
1
Tony Woodcock
Reserves:
James Lowe, Charlie Ngatai, Brad Weber, Sam Cane, Luke Romano, Nepo Laulala, Wyatt Crockett, Hika Elliot.
Others:
Tim Nanai-Williams, Jordan Taufua, Liam Messam, Dominic Bird, Codie Taylor