Melbourne - England spinner Graeme Swann is returning home from Australia because of a lower back strain but should be fit for the Cricket World Cup, team coach Andy Flower said on Tuesday.
Swann, who was instrumental in England's first Ashes series victory in Australia for 24 years, was already struggling with a knee injury he suffered while batting in the one-day series.
"Graeme Swann will be taking the earliest flight home," Flower told reporters in Adelaide.
"He's unfortunately got a strain in his lower back and that, allied with his knee problem, means that it is best for him to go home and get ready for the World Cup now.
"Of course it is a big blow, he's an important part of our side, he's a world class performer and he's full of confidence obviously after the Ashes. But these things happen.
"We are coming towards the end of a long, hard tour and certainly the physical challenges are starting to take their toll."
Flower said he was confident both Swann and seamer Tim Bresnan, who has also returned to England with a torn calf muscle, would be ready to play at the World Cup, which starts next month in India, Sri Lanka and Bangladesh.
Paceman Stuart Broad, who missed the last three Ashes Tests with a torn abdominal muscle, has rejoined the squad but is unlikely to feature in the remaining four matches of the series against Australia, which England trail 3-0.
"It is good to have him out here with the squad again," said Flower.
"He is going to be an integral part of our World Cup campaign and having him out here, training with us, and working with out sports science people is where he should be."
The fourth one-day international against Australia takes place at the Adelaide Oval on Wednesday.