Yamaha's Ben Spies has been ruled out of the Phillip Island MotoGP round this weekend after scans showed he has injured his shoulder, cracked a rib and suffered bruising in Sunday's Sepang crash.

Spies believed he had escaped relatively unscathed from the incident but after going to a Kuala Lumpur hospital today, it was revealed he had an AC shoulder separation, a cracked rib in the upper chest area and bruising to the lung.

"I'm lost for words. We've had such a tough season with an unbelievable amount of bad luck. We have always gone out there to give it 100 per cent and it was the intention of both myself and my team to continue to do so at Phillip Island," said Spies, who will not be replaced in Australia.

"I took a really hard knock on Sunday and it's now clear from today's tests that I have some injuries that require immediate attention.

"It's disappointing to be heading back to the USA now instead of to Phillip Island but it's obviously important to get the right treatment as soon as possible.

"I'm sorry for my team and thankful for all the hard work they and Yamaha have put in so far; our current situation is not where we should be."