Moto2 veteran Dominique Aegerter will sit out next weekend's Jerez round after he sustained a cracked pelvis in a training accident.
The Swiss rider fell sideways while riding his enduro bike on Thursday, hitting a stone and suffering a fissure to his pelvic bucket.
While Aegerter avoided a total fracture, he will still have to undergo surgery on the injury, ruling him out of competing in Jerez on May 4-6.
Kiefer Racing therefore may be forced to skip the Spanish round entirely unless it is able to find a replacement for its sole rider Aegerter at short notice.
The team underwent a major overhaul over the winter following the sudden death of co-owner Stefan Kiefer late last year, switching from Suter to KTM machinery.
It was forced to downsize to a single bike for Aegerter, who sits 10th in the standings after three races with a best finish of eighth in Argentina.