yes. the only way you can get cover for the driver, is for him/her to have his/her own personal accident policy. mind you, some comprehensive motor policies might give some small token payment for medical expenses. however, this can be as low as €100.
payment is made under Third party part of the policy to the party that the driver injures. In theory, the innicent Third party sues the culpable driver and is awarded money against him. teh insurance company then indemnifies the driver and pays the money on his/her behalf. As you cannot sue yourself, the culpable driver cannot sue himself.
having said that, if you are of the opinion that he hit a rock on the road, how did the rock get there, whoever left it there or caused it to be there, may have a liability. However, you would need engineering advice/evidence, independent witnesses and legal advice.