Colin Edwards saw his hopes of a Motegi podium end before the opening lap, when he raised his hand to acknowledge some form of technical problem.
The Monster Yamaha Tech 3 team remained tight lipped as to cause of the Texan's difficulties, rumoured to be electronic related, but Edwards - who had slumped to last by the end of lap two, kept his composure and eventually regained pace.
Aided by accidents ahead, Edwards worked his way up twelfth place by the flag, setting the sixth fastest race lap in the process.
“That was not at all what I expected but I can't turn the clock back. I wish I could because I believe I could have fought for the podium,” said Edwards. “We had a small issue at the start of the race and I simply couldn't ride how I wanted to.
“I kept my head down and persevered throughout and perhaps a few more laps I could have chased down the guys in front for a top ten. I couldn't have ridden any harder today and I did my absolute best for Yamaha.
“When I got going in the race my lap times were as quick as the top five, so it's a case of wondering what might have been today. We'll look to bounce back in Jerez next weekend because I feel like I'm riding really well.”
“I'd like to thank Colin for his efforts today in difficult circumstances,” said team manager Herve Poncharal. “He had a problem before the start and we are still investigating the cause with Yamaha. But his pace in the second half of the race was very impressive, so we know that Colin is in very good form heading into Europe.”
Team-mate James Toseland finished ninth.