Hector Barbera will not be sufficiently fit to return to his Pramac Ducati for the forthcoming Indianapolis round, where he will again be replaced by Toni Elias.
Barbera broke his leg in a training accident and, three weeks' after surgery, returned to Barcelona's Instituto Universitario USP Dexeus on Thursday for a check-up.
The Spaniard has been given the all-clear to begin active physical therapy - in both the swimming pool and the gym - and is now targeting the Brno round, from August 24-26, for his MotoGP return.
“Firstly, I want to thank everybody for all their messages of support since the day of my surgery. The support and love has been overwhelming and it has been a great comfort to me at this difficult time,” said Barbera.
“I'm undergoing rehab on my leg; the situation is improving. It's been three weeks since the operation, and yesterday, Doctor Mir evaluates my physical progress.
“Now I'm able to give the leg an active workout, in the pool and in the gym, to get ready for the 12th round of this season in Brno.
“I will have to work as fast as I can, but I hope to be in good shape for the Grand Prix Ceské Republiky.”
Former MotoGP race winner and Moto2 champion Elias was called up to replace Barbra at Laguna Seca, having recently split from the Aspar Moto2 team.
Elias, who took two podiums for the team in 2008, qualified 17th then crashed out early in the race.
Barbera, who claimed his first ever MotoGP front-row start at last weekend's Mugello round, has taken a best race finish of seventh on the original 'Valencia-spec' version of the GP12 so far this year.
The Indianapolis round will be held the week before Brno, from August 17-19.