Penrith centre Waqa Blake will miss at least the next four weeks after scans confirmed the 23-year-old suffered a high-grade syndesmosis injury in the Panthers' win over the Eels on Sunday.
Blake was tackled late in the game and suffered the injury in the final stages of the contest, before scans confirmed the extent of his pain.
The centre will miss a minimum four weeks, and will soon meet with a specialist to determine whether he'll need surgery, and if his time on the sidelines will be longer than expected.
Penrith coach Anthony Griffin will name Blake's replacement on Tuesday when the Panthers' team list is revealed.