England batsman Kevin Pietersen is to have a scan and an injection in his right knee after an old injury flared up.
The Ashes start on 21 November and the latest problem for Pietersen will be a source of concern to head coach Andy Flower.
Wicketkeeper Matt Prior is also carrying an injury and will have a scan on his left calf ahead of England's final warm-up match against an Australian Invitational XI at the SCG, which starts on Wednesday.
Instead of traveling with the rest of the touring party to Sydney, Pietersen will fly to Melbourne for medical treatment and a prognosis, although he has already stated on social network: "I am fine - #relax."
Knee problems forced the Surrey batsman to miss three months of competitive cricket, including the final Test of England's drawn series in New Zealand and the Indian Premier League.
He also sat out the two Tests and three ODI's against the Kiwis at home, in addition to the Champions Trophy, before returning to help England defeat Australia 3-0 in the home Ashes series this summer.
Despite the latest injury setback, Flower was keen to play down the problem, insisting Pietersen should still play a key role in England's Ashes defence.
"Kevin has had a slight recurrence of that knee issue, and he'll be going to Melbourne for a scan and a cortisone injection, so he won't be travelling with the rest of the team," he said.
"I don't think it's going to be a huge issue. He's had a couple of these injections before, and they've been successful.
"They've quietened the problem down, and it's obviously an ongoing issue for him. We anticipate this one being successful and him playing a full part in the Ashes tour."
Flower must also wait to find out the severity of Prior's calf problem, with the Sussex player a mainstay of the England team and vice-captain to Alastair Cook.
"He is a concern. He's tweaked something in his calf," added Flower.
"We're not sure of the extent of the injury as yet ... he will obviously need a scan."
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