New Zealand captain Sam Cane and hooker Dan Coles have been ruled out of their autumn tour, which starts against Wales in Cardiff next Saturday.
Cane fractured a cheekbone as the All Blacks struggled in Saturday's 38-31 win over Japan.
Coles is also out of the three-match tour - in which they will face Scotland and England too - after calf problems recurred in the warm-up in Tokyo.
New Zealand have called in flanker Billy Harmon and hooker Asafo Aumua.
However, Foster has yet to name a new tour captain, saying: "We've got an answer, but we've got about three different flights and team players all left late last night or early this morning so I haven't had a final conversation with the person.
"I'm just going to reserve that for a day, but it's all sorted."
Cane played on in Tokyo despite realising he had suffered the injury with 10 minutes left.
Hospital tests later confirmed a double fracture around and eye socket
"Without having done my cheekbone before, I knew I had probably done my cheekbone," Cane told allblacks.com.
"I could feel it when I put my hand on my head. And I could feel the blood in my mouth. It was sort of sore but numb at the same time.
"The game was in the balance at that point, and it didn't restrict my ability to play and perform so I was happy to carry on."
New Zealand are already without Sam Whitelock, Will Jordan, Folau Fakatava and Leicester Fainga'anuku through injury and tour withdrawals for the tour that also includes games against Scotland and England.
Wales have not beaten New Zealand since 1953.