If you clarify what you want to do (restore, update, or boot another OS), I can give more specific steps.

Because it runs an Intel Atom chip, the Nexus Player is technically an x86 device. This means it shares architecture with PCs. In theory, you could boot a lightweight Linux ISO (like Alpine Linux or a very old Ubuntu for Intel Atom), but you will lose hardware acceleration for video decoding. For streaming Netflix or Plex, this is a dealbreaker.