Seoul, South Korea ? Look for the United States to make some lineup switches against South Korea on Monday.

Earnie Stewart appears doubtful, Claudio Reyna seems hopeful and Kasey Keller could take over for Brad Friedel in goal a rotation U.S. coach Bruce Arena might have determined before the start of the tournament.

“We have some injuries and there are some other players that can possibly come back,” Arena said Friday, “so it is obvious there’ll be some changes.”

Stewart strained his left groin Wednesday in the opening 3-2 win over Portugal and was replaced at halftime by Cobi Jones. Arena said his options at right midfield include Jones, Eddie Lewis, Frankie Hejduk and Joe-Max Moore.

Reyna, the U.S. captain, missed Wednesday’s game because of a strained right quadriceps, but the midfielder is hopeful of playing Monday.

“He hasn’t tested it fully yet,” Arena said. “We’ll get that opportunity tomorrow.”

Arena won’t say when Clint Mathis will get into a game. The coach has said he doesn’t think the charismatic attacker, who has had knee pain, can go a full 90 minutes, but says he anticipates Mathis will get an opportunity sometime during the tournament.

While the opener was played in the evening in the Seoul suburb of Suwon, Monday’s game is in the afternoon at the southern city of Daegu, which means the temperature could be in the 90s with high humidity.

“I think our players are fit enough to deal with the heat and the humidity,” Moore said. “Our fitness has always been one of our positives. We’re a very athletic, very fit team, and I think we will be able to do that for the full 90 minutes without a problem.

“I have been impressed with their fitness, though.”

Thus far, the Americans have escaped the team dissension that enveloped them in 1998, when they lost to Germany 2-0 in their opener and veterans started to criticize coach Steve Sampson for their lack of playing time.

Sampson made five lineup changes for the second game, against Iran, but the United States still lost 2-1.