As injuries pile up on both sides, the United States and Portugal will limp into their pivotal Group G matchup Sunday.

The United States was dealt a serious blow Thursday when the team announced Jozy Altidore will miss Sunday’s game at Arena Amazonia in Manaus. The 24-year-old Sunderland striker suffered a left hamstring injury during the Yanks 2-1 upset over Ghana earlier this week, but could return in the final group game against Germany. He’s totaled 22 goals in 70 appearances for the U.S.

U.S. forward Clint Dempsey also broke his nose against Ghana, and has the option to wear a protective mask to prevent further injury. The captain tied the record for the fifth fastest goal in World Cup history, putting the U.S. up 1-0 in the first 30 seconds of play, well before defender John Brooks came up with this thrilling header wonder goal in the 86th minute.

Meanwhile, the status of Portugal and Real Madrid superstar Cristiano Ronaldo is also up in the air, with conflicting reports indicating he may be risking his long-term career should he play with a serious knee injury.

Coming off a crushing 4-0 loss to Germany to open the World Cup, Portugal will already miss top defender Pepe, who was issued a red card following a headbutt to Thomas Muller during the letdown, and the loss of Ronaldo puts the country’s hopes of advancing in dire straits.

Ronaldo ended his latest term in Spain by guiding Madrid to a Champions League and Copa Del Rey title, and the wear and tear on his knee seems to have caught up with the 29-year-old.

Portugal’s team doctor reportedly told Ronaldo to rest his knee or risk long-term damage, to which Ronaldo said: “I’m the one that says whether I’m playing or not,” according to Spanish online newspaper El Confidencial.

Ronaldo’s courage and love for his country is certainly shared by at least one of his teammates.

''Cristiano is 100 percent fit to play. Every match, if he starts to play, it is because he is fit to play, he's ready to play,'' reserve Portugal goalkeeper Beto said. ''He loves football but his body is the most important thing for him ... so if he starts a match he is ready, he is fit, so I don't think that is a problem.''

A win for the U.S. puts them right behind Germany and into the Round of 16, and knocks Portugal out. Seleccao need a victory or draw to stay alive in the tournament, or risk joining Australia, Spain and Cameroon on the list of eliminated countries.

Replacing the talisman Ronaldo is an impossible task for manager Paulo Bento, but a start for forward Heider Postiga may not be out of the question. Joining the national team the same year as Ronaldo, the 31-year-old Postiga has recorded 27 goals in 69 appearances since 2003.

U.S. manager Jurgen Klinsmann must also decide how to exploit Ronaldo’s injury or absence, and who will stand in for Altidore.

Ronaldo’s absence opens up the midfield for the Yanks Michael Bradley and Alejandro Bedoya, and puts more pressure on Portugal midfielders Andre Almeida and Joao Moutinho. Bradley has totaled 12 goals in 86 career caps for the U.S., but could play his stronger role as facilitator and feed Dempsey and possible Altidore replacements Aron Johannsson and Chris Wondolowski.

Johannsson, 23, certainly has the speed and technical skills to compete against the world’s best, totaling 20 goals last term for Holland club AZ Alkmaar.

But experience is more on Wondolowski’s side. The 31-year-old has 21 senior team appearances and nine goals, and has scored 80 goals for MLS’s San Jose Earthquakes over the last five years. Still Johannsson represents the future of the Yanks, and he needs more experience on the international stage.

Date: Sunday, June 22

Start Time: 6 p.m. EST

TV Channel: ESPN

Prediction: U.S. 3-2