Ben Spies struggling with injuries in Malaysian Grand Prix practice

The American had to sit out the Phillip Island race last weekend after he became dizzy during the warm-up. Spies had crashed heavily in qualifying, leaving him with heavy bruising, and said he remained in discomfort after going ninth quickest in afternoon practice at Sepang.

"It's been a really rough day, coming back after the crash in Australia I'm pretty beat up and not able to ride the bike like I want to, which is really showing," said Spies.

"We're doing the best we can but I feel like I'm struggling.

"We'll try to get as many points as we can this weekend and keep a reign on fifth place in the championship."

Yamaha team boss Massimo Meregalli is optimistic that Spies might be in better shape tomorrow.

"Ben is really suffering with his rib injury so it's difficult to expect more from him, he is trying as hard as he can," said Meregalli.

"I think that tomorrow he can maybe deliver some better laps. During qualifying you are more focused and can fight the pain for a couple of hot laps."

Meregalli is confident that the Yamaha is competitive if Spies can get himself up to speed.

"The bike set-up is not so bad," Meregalli said.

"At this moment he can't push hard enough to find any issues or use the full performance of the bike."