All Blacks scrum-half TJ Perenara and England prop Joe Marler are both considered unlikely starters for the second test in Auckland where New Zealand will chase a series sweep.
All Blacks coach Scott Robertson said on Sunday an unnamed player was on standby to join his squad ahead of Saturday's final test of the two-match series.
Perenara appeared to hyper-extend his knee in a collision with a teammate during the first half of Saturday's 16-15 win in Dunedin and did not return after the interval.
"We've got plans in place if he's not right," Robertson said.
"I hope it's one of those ones that looks worse than it actually is."
The 32-year-old was playing his 81st test, 18 months after suffering a serious Achilles tendon rupture in a drawn test against England at Twickenham.
Marler's foot injury ended his 95th test prematurely and he's likely to miss the Eden Park decider, according to coach Steve Borthwick.
"A man as tough as Joe leaving the field clearly means it is not just a small injury. It's not just a bruise," Borthwick said.
"We don't know the full extent of it, but clearly it doesn't look good for next week."
DEBUT FOR FIN
Marler's exit heralded a 63-minute debut off the bench for Fin Baxter, although the Harlequins prop struggled to stabilise a wobbly England scrum.
Borthwick said the scrum was one of several areas that would need addressing but refused to blame three missed shots at goal from fly-half Marcus Smith for the defeat.
"Everyone makes mistakes and Marcus also produced magic on that pitch today," he said.
All Blacks fly-half Damian McKenzie registered the same two-from-five goalkicking return, including being "timed out" when taking longer than 60 seconds to attempt a late penalty goal.
McKenzie called for a shot clock to be installed on the big screen at New Zealand venues.
"I can't always count to 60 in my head, especially when I'm trying to focus. I just missed the time," McKenzie said.
England must defy history to square the series at Eden Park, where New Zealand have not lost a test since 1994.
England are also chasing their first win over the All Blacks on New Zealand soil in 21 years.