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.
He will be replaced by Grenoble wing Daniel Kilioni, who is awaiting a visa to join up with the squad in Japan.
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.
When will Tonga play next at the Rugby World Cup?
Tonga are in the so-called "Pool of Death" with games against England, Argentina, France and the USA. It will be a tough challenge for the team in red.
So when are the games on?
Tonga have already played England, losing 35-3.
The second game is against Argentina on Saturday September 28 at 1.45pm Japanese Time. The game will be played at the Hanazono Rugby Stadium
That means the local timing of the match is:
Nuku'alofa: Saturday 5.45pm
Auckland: Saturday 4.45pm
Sydney: Saturday 2.45pm
Tonga will play its third pool match against France on Sunday October 6 at 4.45pm, Japanese Time.
Nuku'alofa: Sunday 8.45pm
Auckland: Sunday 8.45pm
Sydney: Sunday 6.45pm
A week later it will play USA on Sunday October 13 at 2.45pm, Japanese Time
Nuku'alofa: Sunday 6.45pm
Auckland: Sunday 6.45pm
Sydney: Sunday 4.45pm
When will the final of the Rugby World Cup be held?
The final of the 2019 Rugby World Cup will be held in Yokohama on Saturday, November 2 at 6pm.
The kick-off in local times will be:
Nuku'alofa: Saturday 10pm
Auckland: Saturday 10pm
Sydney: Saturday 8pm