Can I ask a potential sitter to provide references?

I found a potential house sitter near my home. I chatted with him over the phone asking for two references. The sitter said he cannot provide contact information for his rover clients citing privacy concerns. I asked him to get their permission first and have any clients or neighbors to vouch for him. He refuses to provide any references. This is a deal breaker for me. Before I contact another person on Rover, can someone clarify whether asking for references is uncommon?