Seoul, South Korea ? The United States has been aching for four years to show the world it’s no longer a last-place team. Now, on the eve of its World Cup opener, the United States is just plain aching.

Captain Claudio Reyna has a strained right quadriceps and star attacker Clint Mathis has inflammation in his left knee going into Wednesday’s game against Portugal in the Seoul suburb of Suwon. Reyna is unsure either of them will play.

“We will see how he feels today and tomorrow,” coach Bruce Arena said today of Reyna. “Whether you realize it or not, there are a lot of players in this tournament who are not 100 percent. I think he’ll be able to make the adjustments that are necessary.

“If Claudio is on the field, we really believe he is going to help us win.”

Arena played down the severity of Mathis’ pain, saying he was told Mathis could play. But he didn’t exactly give Mathis a ringing endorsement today before the team worked out at Suwon Stadium.

“Clint’s worked very hard with us the last 30 days,” Arena said. “He’s going to position himself to help us at some point.”

Reyna’s leg appeared more troubling. The midfielder missed the 1994 World Cup because a pulled right hamstring and has a history of health woes.

“We have been so used to injuries that we have rarely played with our whole starting group over the last few years,” Arena said. “One thing about this team is that we are always prepared to make adjustments.”

Even with everyone healthy, the United States would have a tough task against Portugal, ranked fifth in the world and led by stars it has dubbed the “Golden Generation.”

In their final preparations for the World Cup, the Americans also lost Chris Armas, their best defensive midfielder. If Mathis can’t start, the United States could wind up opening with its two youngest players, DaMarcus Beasley and Landon Donovan, both 20.

Arena won’t disclose his starting lineup, and players said they didn’t know, including goalkeepers Brad Friedel and Kasey Keller. Arena has rated them even, and following knee and elbow injuries to Keller in the past three weeks, Friedel appeared to be the favorite to get the start against Portugal.

The defense likely will have Jeff Agoos and Eddie Pope in the center, with Tony Sanneh and either Frankie Hejduk or David Regis on the outside. John O’Brien and Earnie Stewart and probably Beasley will be in the midfield, with the other spot uncertain if Reyna can’t play. Brian McBride is likely to start up front with Mathis or Donovan.

Reyna was hurt last week in one of the first practices after the Americans arrived in South Korea, but the severity of the injury wasn’t clear. He resumed training on Saturday, but the leg still hurts when he shoots or makes long passes.

When he played in the qualifying rounds, the Americans were 6-1-2. When he was sidelined by injuries or suspension, the U.S. team was 2-3-2.

“I’m upset. I’d rather not be injured. I’d rather do everything 100 percent,” Reyna said.

Arena said Sunday that Mathis had been slow to recover from tearing his right ACL last June 5. But the knee that is hurting now is his left, operated on after Mathis tore that ACL during an NCAA tournament game for South Carolina against Coastal Carolina on Nov. 19, 1995.

“He practiced briefly today. We took a precautionary MRI and found nothing,” Arena said.

So, on the verge of their biggest game in four years, the Americans’ lineup seemed just as uncertain as it did in France, where five starters were changed between the opening 2-0 loss to Germany and the 2-1 loss to Iran that eliminated the United States.

Back then, players blamed coach Steve Sampson, who quit four days after the U.S. team finished play.