Spain's Sete Gibernau had an operation on his fractured collarbone yesterday and will be replaced by Germany's Alex Hofmann at Saturday's Dutch MotoGP race, his Ducati team said.
Hofmann, 26, has been riding a non-works Ducati for the Pramac d'Antin team this season after three years with Kawasaki.
Gibernau, who suffered the injury in the Catalan Grand Prix in Barcelona on Sunday, had a titanium plate put in to replace a metal one which had been inserted after a previous incident.
Italian team-mate Loris Capirossi, also involved in the six-rider crash in Barcelona, will compete at Assen. Capirossi was kept in hospital overnight and then returned to his base in Monte Carlo. The team said he was already on his way to Assen.