Casey Stoner blamed tiredness for his defeat in the San Marino Grand Prix, saying his energy level plummeted in the second half of the race.
After challenging title rival Jorge Lorenzo for the lead at first, Stoner lost touch with the Yamaha and found himself slipping to third behind his Honda teammate Dani Pedrosa. Stoner said he had felt entirely comfortable early on, even when drizzle was hitting the circuit, and that the issue was with his fitness rather than the bike or its set-up.
"The bike and everything felt pretty good," he said. "We were pretty happy with the way the bike was performing - especially at the start of the race when we normally feel a little bit more uncomfortable.
"We were just sitting behind Jorge because there was a bit of water and we didn't really want to be the first one hitting the wet patches. So I was comfortable behind Jorge and then of course it dried up. We both started running faster lap times and it felt like the bike was working really well and we'd hit a good setup.
"Then maybe halfway through the race, when I felt like I was starting to get a feel for things, all of a sudden I started getting tired. I was struggling on the brakes, ran wide a couple of times, and then started braking earlier, which lost me more time.
"It just sort of built from there. I tried to keep a nice constant pace - I wasn't ever going to be able to catch Jorge again, but wanted to at least stay in front of Dani. But just trying to keep that pace made me more and more tired."
Stoner does not think today's problem was a sign of a significant issue and is sure he will be at full fitness for the Aragon Grand Prix.
"I think after these last few races, a few bad nights' sleep between Indy and now didn't really help," he said. "For the next race we'll be fine again. But it was a tough race today."
He also paid tribute to Lorenzo after the Yamaha man's first victory since the start of July.
"Hats off to Jorge, he rode a great race, and didn't make any big mistakes so he was able to pull away at the front," said Stoner. "We'll be ready again at the next one."