Rob Herring is en route to Japan as Sean Cronin's replacement after the Leinster hooker suffered a training ground injury this week.
Cronin becomes the second Ireland player to have to go home due to injury, following Jack Conan's departure after the loss to Japan.
The 33-year-old came off the bench after 58 minutes of that clash with the hosts in Shizuoka.
Cronin also came off after 50 minutes of the victory over Russia in Kobe.
The latter was his 72nd cap but he was not expected to make the bench as cover for skipper Rory Best for Saturday's World Cup quarter-final against the All Blacks, with Niall Scannell set for that role.
Ulster stalwart Herring, 29, has eight Ireland caps spanning the last five years.
