Somerville will be replaced in the 35-man All Blacks squad by Auckland's Saimone Taumoepeau, with coach Graham Henry having made an earlier enforced change this week when injured back Luke McAlister pulled out because of a knee injury and was replaced by Nick Evans.
Henry admitted the decision regarding Somerville was touch and go, and the Crusaders prop had every chance of going until failing a last-minute fitness test.
On McAlister's condition, Henry said: "He's gutted obviously.
"But what can you do? You just have to get on with it and he will set his sights higher for next year. He's a quality footballer and he's proved that."
Henry added the injury sustained by lock Ali Williams would prevent him from the side to play Wales in the tour opener, but not exclude him from touring.
"He got tackled in touch rugby and did some damage to his shoulder, which is disappointing," Henry said.
"He'll be fine for the second Test on tour. He's on the mend and mending pretty quickly."
The All Blacks launch their four-Test trip against Wales in Cardiff on Saturday week, followed by appointments with Ireland, England and Scotland.