Loris Baz will miss this weekend's Misano MotoGP round following further medical checks and be replaced at Avintia Ducati by Xavi Fores.
Baz and Pol Espargaro were involved in a huge first lap accident in Sunday's Silverstone race, prompting a restart.
Doctors at the track reported only a sprained ankle for the Frenchman, but further scans and an MRI in Switzerland found a fracture on his lower tibia and another on the astragalus of his right foot, plus bruises, small pieces of bone and some damaged tendons.
With surgery not possible, Baz's leg has instead been immobilised, meaning he cannot ride this weekend. Baz previously missed two rounds due to fractures in the same foot, when he was taken out at turn one of the Italian Grand Prix.
“The news I got once I came to visit my Doctors in Switzerland is a real shame, and unexpected," Baz said. "But after several tests, they saw some fractures on my right foot. The main fractures are on my tibia and astragalus. Surgery is not possible and it will just take time and rest to heal. So I'm forced to miss Misano. Anyway, I'm still fortunate to not have serious injuries following the crash at Silverstone.
"I feel bad and sorry for my team, because we were coming back and improving in the last few races. It's a shame, but I'll try my best to come back as soon as possible and finish the year in the best possible way. This was another hard blow in my season after the one from Mugello, but I have to be positive and look forward."
Ducati test rider Michele Pirro replaced Baz while he was injured earlier in the year. But since Pirro already has a wild-card entry with the official team this weekend, Avintia has instead called up Fores for a surprise MotoGP debut.
"I wish Xavi the best for this weekend," Baz said. "MotoGP bikes are incredible, and I'm sure he'll enjoy it a lot. He'll also have a great team behind, and I'll be there in case he needs any advice. I'm sure he won't forget the experience.”
The Spaniard made eleven previous Moto2/125cc starts, either side of a spell in World Supersport and is currently competing in World Superbike for the Barni Ducati team.
Fores has claimed four fourth-place finishes so far this year and holds tenth in the championship standings.
“I'm really happy for this opportunity with the Avintia Racing team. I'm sure this will be a positive experience for me," Fores said. "My aim is to enjoy it to the maximum and leave the pressure at home. I have nothing to demonstrate, the bike is completely different to anything I've ridden before. I have to be clever because everything will be new for me, so I only want to enjoy it.
"Riding a MotoGP bike is a dream for every rider, and I'm looking forward to start the weekend to live the experience. It will be crucial not to make any mistakes and not get hurt, because I have to race in Germany next week with my WorldSBK team. I'll use this weekend like a training session before my next race, and I'll try to enjoy as much as possible riding the MotoGP bike.
"Misano is one of my favourite circuits and I got my best results so far this season in WorldSBK. So it is the best possible scenario to start to work with an unknown bike. I what to say big thanks to Avintia Racing, Ducati and specially my team, Barni Racing for letting me race. And I also want to wish Loris a fast recovery. Keep calm, I'll take care of your BabyDesmo!”
Espargaro also escaped serious injury in Sunday's incident and plans to ride this weekend.