Argentina centre Gonzalo Tiesi has been ruled out of the 2011 Rugby World Cup and captain Felipe Contepomi struggling with bruised ribs after a crunching opening defeat to England.
Tests early on Sunday confirmed Tiesi's tournament was over after he came off 37 minutes into the narrow 13-9 loss with an injury to his right knee, a team spokesman said.
Captain and fly-half Contepomi is also in doubt for Argentina's second game against Romania after leaving the field in the first half with a rib injury, although tests showed there was no serious damage.
"There is no fracture. It's only bruising. He is in a lot of pain and we will just have to see how it goes," said the Pumas' assistant coach Fabian Turnes.
"We will wait till tomorrow (Monday) to see whether he will be able to play against Romania."
A regular succession of Puma replacements during the Pool B encounter bore testament to the ferocity of the English tackling as Martin Johnson's men gradually wore down the South Americans to win with a late Ben Youngs try.
That puts them in pole position to top a group that also includes Scotland, Romania and Georgia, which would mean most likely they would avoid going up against the All Blacks in the quarter-finals.
But the result also leaves Argentina facing a must-win game in Invercargill next Saturday if they are to keep their hopes alive of reaching the last eight.
A prolonged spell on the sidelines for Contepomi would be a big blow for the Pumas as they lost regular fly-half starter Juan Martin Hernandez before the World Cup got underway with a knee injury.
But Turnes ruled out the idea that Hernandez could be called up to replace Tiesi, as he has yet to return to action for his French club side Racing-Metro.
Tiesi's replacement was not immediately named.