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RUSTENBERG, South Africa (AP) — Frank Lampard has a warning for the United States.

Lampard says England star Wayne Rooney is no-longer the hotheaded striker whose ejection at the 2006 World Cup helped lead to his team's elimination in the quarterfinals.

Since stamping on Portugal's Ricardo Carvalho, fatherhood and marriage have been credited by both England coach Fabio Capello and Manchester United manager Alex Ferdinand with helping mature the 24-year-old Rooney.

So Lampard was surprised Saturday to hear that former U.S. defender Alexi Lalas was advising the Americans in their World Cup opener against England next Saturday to antagonize Rooney.

"Everyone has seen his maturity as a player and a person over the years," Lampard said. "I don't think there is any issue about trying to wind him up."

Capello has lectured his players on the importance of not allowing a reckless moment to jeopardize England's hopes of a first World Cup title since 1966.

"Discipline is important at any level of football," Lampard said. "You have to understand the importance of having 11 men because when you are at the top end, the small details and small changes mean everything. If you get a red card it's a bit stupid and it can affect the team. Referees are looking at these kind of incidents because the world is watching.

"The manager has always spoken about making sure you don't lose your head. Everyone wants to be aggressive in the tackle, but you don't want to overstep the mark and put the team in jeopardy."

The 31-year-old Lampard has a key role in the England camp after being elevated to assistant captain behind Steven Gerrard following Rio Ferdinand's tournament-ending left knee injury.

"I am not a huge socializer around the camp — I have my quiet words and do my thing," Lampard said. "But when we train and play, I am very serious. I will speak to people around me in a quiet way. On the pitch I am a bit more vocal. I won't try and change that."

Lampard was one of the players to go to Ferdinand's room Friday night after scans on the Manchester United center back's knee showed he would be out for four to six weeks.

"He was laid up and very down," Lampard said. "He's coping, it's obviously very disappointing."

But with the United States match a week away, Lampard knows the team must quickly get over the shock.

"We have lost a big player," Lampard said. "But we can't try to make an excuse of that. We just have to keep focused.

"Let's do it for Rio. That has become a bit of a slogan. We want to win it (the World Cup) as a group."

The immediate challenge for Capello is who replaces Ferdinand in the starting lineup against the Americans in this northern South African town.

"It is a blow. Go through the team and most people could name the important players who could have been there or thereabouts for a long time and played regularly. Rio is one of them," said Lampard. "Him and JT (John Terry) have formed a successful partnership for the past few years. Now it is up to whoever steps in, but it is not ideal this close to the tournament."

That man defending alongside Terry could be Ledley King, who, despite chronic knee problems, has been a solid figure for Tottenham, which qualified for the Champions League for the first time.

King, though, struggles to train between matches and, as on Saturday, was restricted to working on his own in the gym. That could limit his ability to quickly forge a defensive partnership with Terry.

"It's not ideal, Ledley would rather train every day," Lampard said. "With top players, of course you need to work on the training ground, but I think a lot can be said that Ledley and John are intelligent enough to understand each other."

Ferdinand's squad replacement, center back Michael Dawson, immediately joined the team on Saturday at training after flying into Johannesburg from London. Another option is Matthew Upson, who missed Saturday's session with a fever that is not thought to be serious.

There was some better news for Capello about goalkeeper David James, who returned to training after struggling with knee problems following the team's flight from London.