Coach Bob Bradley said that he did not know if Howard had sustained broken ribs when England’s Emile Heskey slid into him in the 30th minute of Saturday’s game. Howard received a cortisone shot at halftime and kept playing so superbly that he was named man of the match.

But he was sore when he woke up Sunday, Bradley said. Howard continued to receive treatment Sunday and was to be evaluated Monday morning. A decision would be made whether he would need further tests, like X-rays or a magnetic resonance imaging test, a team spokesman said.

Howard was not available for comment. Asked if he would be available against Slovenia at Ellis Park in Johannesburg, Bradley sounded cautiously optimistic.

“At this time, there is no answer, but when we see the way Timmy handled himself after the collision, we certainly expect he’ll be on the field again,” Bradley said.

If Howard were to miss any time, his absence could threaten the United States’ chances of reaching the second round or advancing deep into the tournament.

He is one of the world’s elite goalkeepers, playing with Everton in the English Premier League. During the 2003-4 season, playing for Manchester United, Howard was named the Premier League’s goalkeeper of the year. On Saturday night, Howard said he was “in agony” after the collision and said that his recovery would “take me a few days” at least.

If he cannot play, he will be replaced by Marcus Hahnemann or Brad Guzan.

“Obviously he was sore,” Bradley said of Howard. “He did a great job of taking a tough hit and staying in and playing really well. But we’ll assess him later today and figure out what we need to do from there.”

As bad as Howard felt Sunday, the English goalkeeper Robert Green could not have felt much better. His huge blunder in misplaying an innocuous shot by Clint Dempsey in the 40th minute has already become one of the most infamous goalkeeping mistakes in World Cup history.

Inevitably, the reaction by the British newspapers was harsh. The Mirror referred to the mistake as “The Hand of Clod,” a reference to the goal scored by Argentina’s Diego Maradona that sent England out of the 1986 World Cup.

The Sun carried a headline playing off of Green’s first name: “Robbed.” The Guardian wrote: “Wanted urgently against Algeria in Cape Town on Friday: a keeper who can hold onto the ball.”

The Sunday Times of London made a reference to British Petroleum and the Gulf of Mexico oil spill, saying that Green’s howler was “one disastrous spill the Yanks won’t complain about.”

The United States made its own mistake in the fourth minute, when a defensive lapse led to a goal after an England throw-in. When the ball came to Frank Lampard, the American midfielder Michael Bradley closed quickly. A pass that seemed aimed for Wayne Rooney skipped past him toward Heskey, who found Steven Gerrard in the penalty area.

But Oguchi Onyewu, playing his first full game in eight months, had already moved toward Rooney, leaving a hole in the American back line between Jay DeMerit and Carlos Bocanegra.

“You have to have the ability to play collectively as a defense, but that also involves keeping track of players,” Bradley said. “If you’re so worried about every player every time and you’re just pushing early to a guy, that means there will be gaps.”

Midfielder Ricardo Clark was left to track Gerrard, but he was a step late and Gerrard pushed a shot past Howard for a 1-0 England lead.

“All it takes in these kind of games is a couple of seconds where the reactions aren’t as good as they need to be,” Bradley said. “You’ve left a hole and you pay.”

While the defense needs more reliable organization, Bradley said, he was pleased with the resilience and individual commitment of Onyewu, DeMerit, Bocanegra and Steve Cherundolo. That performance was reminiscent of the United States’ victory over Spain last June at the Confederations Cup in South Africa.

“Guys were committed to doing that little extra bit, to chase a little bit harder, go to the ground, come away with a tackle,” Bradley said. “That’s what we’ve been able to do at times in the biggest games, like Spain. This one was sort of similar.”

Now the Americans will turn their attention toward Slovenia, which defeated Algeria, 1-0, on Sunday and sits atop Group C with 3 points.

Slovenia, which declared independence from Yugoslavia in 1991, has a population of just over two million, which makes it the smallest country participating in the World Cup. But it has one of the most impenetrable defenses, anchored by goalkeeper Samir Handanovic, who plays for Udinese in Italy’s Serie A.

Slovenia surrendered only four goals in its European qualifying group and defeated Russia in a playoff. Traditionally, the United States has struggled against organized, muscular teams from Eastern Europe. Slovenia is not likely to play the same fast, physical style that England did. Instead, it will probably sit back and look to score on the counterattack.

A player like Jose Francisco Torres might figure in midfield in a match like this, where the Americans will seek to break down a compact, obstinate defense. Compared with Saturday’s game, Bradley said, “This might be a little bit more of a chess match.”