Oakland Raiders rookie quarterback Derek Carr was forced out of Sunday's 38-14 loss to Miami in London because of ankle and knee injuries.
Carr told reporters after the game that he suffered a sprained MCL in his knee and a high ankle sprain.
"I know the X-rays on his ankle were negative, but that's the extent of what I know,'' Raiders coach Dennis Allen said.
The Raiders initially announced Carr was questionable to return, but he never came back into the lopsided defeat.
Carr appeared to be urging Oakland coaches to allow him to stay in the game. However, he was limping noticeably.
Oakland third-string quarterback Matt McGloin finished the game. Backup Matt Schaub has missed the past two games due to a family situation.
Carr, a second-round pick from Fresno State, has started all four games for the winless Raiders. He was 16 of 25 for 146 yards with a touchdown pass and an interception before his injury Sunday.