The Ashes 2013-14: England wicketkeeper Matt Prior ruled out of final warm-up match and is a doubt for first Test in 10 days time

Prior announced on Twitter that he will miss the match against the Australian Invitational XI due to a tear in his calf muscle

Matt Prior has been ruled out of England's tour match against the Australian Invitational XI this week with a calf problem.

Jonny Bairstow will replace him in the side but England remain optimistic that Prior will be fit in time for the first Ashes Test which starts in Brisbane on November 21.

"Matt Prior has been ruled out of the tour game starting on Wednesday with a low-grade tear of his left calf," an ECB spokesman said. "He will continue his rehab and recovery with a view to being picked for the first Test."

The wicket-keeper used Twitter to express his determination to be back in time for the first Test.

"Obviously very disappointed to be missing the game at SCG but doing everything possible to be ready for the 1st Test at the Gabba! #ashes" he wrote.

Like Prior, Kevin Pietersen has had a scan after also giving England an early injury scare.

But with the start of the Ashes only 10 days away, it seems the recurrence of Pietersen's old problem with bone bruising in his right knee - he missed three months earlier this year, and was close to surgery at one point - is not going to disrupt his preparation.

Pietersen was set to take full part in indoor training on Monday at the SCG, where pouring rain stopped England using the outdoor facilities.

Ian Bell was able to confirm his fellow batsman is back on track, having diverted to Melbourne on Sunday - while his team-mates headed direct from Hobart to Sydney - to have a cortisone injection and his scan.

Asked how Pietersen is, and his chances of playing in the four-day match starting on Wednesday, Bell said: "Really well.

"I don't know the XI. But I'd have thought he's definitely up for selection, and would have thought he'll play."