Captain Inoke Afeaki has been left out of the Tonga team for Sunday's Pool D clash with Wales in Canberra despite being cleared of possible concussion.
The flanker was stretchered from the ground during Wednesday night's 36-12 defeat to Italy, having been pole-axed by a mistimed tackle on prop Andrea Lo Cicero in the 56th minute.
After being assessed at the team hotel and at a Canberra hospital, Afeaki was cleared of concussion, but Afeaki has since undergone treatment for damaged knee ligaments.
Afeaki was able to take part in the squad's recovery session in the swimming pool on Thursday, but is in danger of missing the remainder of Tonga's World Cup campaign.
"We are leaving it for two to three days to let it settle and we'll make a decision on how bad it is," Tonga coach Jim Love said.
No 8 Benhur Kivalu takes over as skipper of a team showing five changes to the one that started against Italy, including Stanley Afeaki replacing his injured brother in the back row.
Lock Milton Ngauamo has been replaced by Usaia Latu, while prop Heamani Lavaka is the only member of the front row to keep his place after the Tongan front three were outplayed by Italy.
Viliami Ma'asi and Kisi Pulu come in for hooker Ephram Taukafa and prop Tonga Lea'aetoa.
Sukanaivalu Hufanga is the only change in the backs, replacing Gus Leger at outside centre.
Love admitted that at least five of that beaten side will go into the Wales match hampered by injuries sustained against the Azzurri.
"A lot of our players were playing in front of a big crowd and playing in the atmosphere of a World Cup. It got to them a bit," Love added.
Scrum-half Sililo Martens, who plays his club rugby with Welsh side the Celtic Warriors, expects a physical battle as he bumps into six of his club-mates who have been selected for Wales.
Tonga: P Hola; S Fonua, S Hufanga, J Payne, T Tu'ifua; S Tu'ipulotu, S Martens; K Pulu, V Ma'asi, H Lavaka, U Latu, V Vaki, I Fenukitau, S Afeaki, B Kivalu (capt).
Replacements: E Taukafa, T Lea'aetoa, M Ngauamo, N Naufahu, D Palu, G Leger, S Va'enuku.