Cristiano Ronaldo could miss the remainder of the 2014 World Cup because of a knee injury.

With 90 minutes remaining in Portugal’s recent training session, the team’s star player was forced to sit on the sidelines. He was seen being tended to by the team doctor and wearing an ice pack on his knee.

Ronaldo had seemingly recovered from the injury prior to Portugal’s match with Germany. Now, he could be done after just one contest.

According to El Confidential, Dr. Jose Carlos Noronha has told Ronaldo to sit for the rest of the tournament, warning him that his career could be at risk. The doctor has reportedly recommended two months of rest for the forward, who’s suffering from patellar tendonitis on his knee. Following the doctor’s order would keep Ronaldo out beyond the World Cup final, which is scheduled for July 13.

An initial report claimed that Ronaldo insisted he would play on, but the Real Madrid star might end up listening to the medical advice he’s been given.

Rumours - unconfirmed may I add - here in press centres in Brazil that Cristiano Ronaldo is out of the World Cup. â€” Ewan MacKenna (@EwanMacKenna) June 18, 2014

No Ronaldo could be a huge break for the U.S. men’s soccer team, who is set to play Portugal on Sunday. Portugal was a heavy favorite in the match, before the news on Ronaldo’s injury broke.

It’s devastating news for Portugal, who needs to do well in their final two group stage contests if they hope to make it to the Round of 16. They suffered a 4-0 loss to Germany in the opener, and likely need a victory over Team USA.

''I would be the first to tell the coach if I were unable to play. I would never put my career at risk even for a World Cup,'' Ronaldo before Portugal’s match with Germany, when he thought he had recovered from his injury.

Now, it might be time for Ronaldo to back up his statement.