HMC/KTM RC8R Superbike rider Chris Fillmore has been ruled out of the AMA Pro National Guard Superbike event this weekend at Mazda Raceway Laguna Seca due to a concussion he suffered in a strange crash during the first practice Friday afternoon.

“It’s not been officially diagnosed,” said HMC/KTM Team Owner Mitch Hansen, “but we think he suffered a mild concussion, and because of that we’re going to hold him out. We’re not going to take any chances.”

Fillmore was running in the top 10 late in Friday’s practice when he crashed in between Turns Four and Five, a section of the track that is normally taken at wide open throttle in higher gears.

Witnesses to the crash could not be found, but AMA Pro Superbike Champion Josh Hayes told Roadracingworld.com that he saw fresh, curving tire marks on the track preceding the scene of the crash. Those marks combined with the wide-open nature of that section of the track indicate that a mechanical issue may have led to the crash, but Hansen said he could not confirm the cause of the crash.

“We don’t know yet,” said Hansen. “Chris couldn’t remember what happened, and we haven’t been able to retrieve the data because the dashboard is just smashed.”