What is the burden of proving that there is an administrative remedy available to a plaintiff?

The court finds that defendants have carried their initial burden of proving the availability of an administrative remedy. Therefore, the burden shifts to plaintiff to come forward with evidence that there was something in his particular case that made the existing administrative remedies effectively unavailable to him or that he has otherwise properly exhausted his claims with respect to the remaining defendants who were not named in his grievance. Williams v. Paramo, 775 F.3d at 1191.