Tonga have lost two of their most experienced players to injury in first five Kurt Morath and utility back Nafi Tuitavake, who have both been ruled out of the rest of the Rugby World Cup.
Morath has been replaced in the squad by Latiume Fosita after picking up a throat injury in the weekend's 35-3 loss to England.
He was hospitalised in Sapporo and is awaiting confirmation on whether he needs surgery or not.
Morath copped a stray boot when attempting to tackle England powerhouse midfielder Manu Tuilagi.
Nafi Tuitavake, who came on as a half-time replacement for wing Atieli Pakalani, broke his left arm late in the match.
A replacement has yet to be named for him.
Tonga assistant coach Pita Alatini said it was obviously desperately disappointing for both Morath and Tuitavake.
"They have worked so hard to be here, but it means there are opportunities for others now."
Tonga's next Pool C game is against Argentina in Hanazono on Saturday.