Good luck trying to find a Nexus Player after today.
Google has quietly stopped direct sales of its set-top box, meaning you'll have to buy it from third-party retailers that still have some stock left. The Nexus Player can no longer be found on the Google Store, but Google issued a statement about it still being available on some retail sites.
The device, which is shaped like a hockey puck and manufactured by Asus, debuted in 2014 as the first set-top box running Android TV, but now it faces stiff competition from not only other boxes and televisions that come pre-loaded with Android TV (such as the Nvidia Shield and 2016 TVs from Sony and Sharp), but also Google's own Chromecast, which is available in the form of a HDMI dongle and TVs with built-in Google Cast.
The Nexus Player was a little media streamer that simply introduced Android TV at a low price. It wasn't powerful enough to run heavy apps or games, and so it certainly didn't showcase Android TV. Keep in mind Android TV is still alive and well. We're assuming Google is either getting ready to replace the device with a new one, or maybe it'll let third-party manufacturers take the wheel.
Xiaomi, for instance, recently announced it is developing an Android TV media streamer that supports 4K content.