By Phil McNulty
Chief football writer in Baden-Baden
Striker Wayne Rooney may make a shock World Cup debut for England against Trinidad and Tobago on Thursday.
Rooney joined in the warm-down after England's win over Paraguay
England coach Sven-Goran Eriksson has not ruled out the possibility of Rooney making a return to action in the match.
"I'm very optimistic, always. I'm born like that. We have to decide that day by day, to be honest," he said.
Rooney, 20, returned to full training last Thursday after a scan showed his broken metatarsal bone was healed and he is now trying to gain match fitness.
Manchester United boss Sir Alex Ferguson will be furious if his striker does make his World Cup debut in Nuremberg.
Ferguson wanted Eriksson to keep Rooney safely on the sidelines until the knock-out stages of the World Cup but the pair did not agree.
Rooney trained on Sunday, along with the other England players not heavily involved in Saturday's 1-0 win against Paraguay.
England defender Rio Ferdinand has revealed Rooney's determination to make an impact on the World Cup.
Ferdinand said: "He's in good spirits. He's doing well and hopefully he will be able to play a part in a few games. He's looking good in training."
England's fans gave Rooney a rapturous reception when his face flashed up on the giant screen, suspended from the roof during the game against Paraguay.
Rooney then joined the other members of the squad for some work on the pitch after the final whistle before returning to join his victorious colleagues in the dressing room.
And Ferdinand revealed his United team-mate was in ebullient mood after the game.
He said: "I heard the chants. He was desperate to get on the pitch, it's the exuberance of being a young chap.
"If you ask any of the subs they would have been desperate to come on.
"The fans know. They love him and he's a great player."
Ferdinand says England team-mate Rooney is desperate to play in Germany
Eriksson must also decide whether to keep faith with Michael Owen, after he was taken off in the 55th minute in their opening Group B win in Frankfurt.
But Ferdinand has no doubts the injury-troubled Newcastle striker will deliver the goods in Germany.
He said: "Michael's all right. I thought he worked hard.
"He did a lot of running in the channels and I thought he caused problems for them.
"If he had a bit of luck with the run of the ball he would have had chances to score a goal but the pitch maybe didn't help him.
"Michael will be fine. He's got nothing to prove when it comes to these big tournaments."