You can choose a doctor that you or any immediate family member has treated with in the past to treat you for your workers' compensation injury.
The doctor that your employer or their insurance company attempts to send you to does not have your best interest in mind. They are paid very well by the insurance company to minimize your injuries and treatment or in many cases to simply state that they do not believe you have an injury.
Remember that nurse case managers are paid well by your employer's insurance company or a company hired by your employer's insurance company to minimize the cost of your case. They minimize the cost of your case by attempting to minimize your treatment with your medical providers by getting doctors to reduce or change your treatment plan to cut costs.
If your workers' compensation claim is denied, your health insurance plan is required to pay for the medical bills related to your denied claim. Further, if your claim is denied, you can treat with any doctor, it does not have to be with a doctor that you have treated with previously.
If a third party, a person or entity other than your employer, caused your injury, they can be held civilly liable and you can recover damages for medical bills, lost wages and pain and suffering from the third party.