I downloaded 'Unity Web Player' but I can't get it to open!?

I just bought the game ‘Rust’ yesterday but I haven’t been able to play it and I downloaded unity web player so it can run but I try to open it and it just starts downloading again, why is that? and how do I fix?

try this , it is a full pack of unity webplayer:
Windows, full: http://webplayer.unity3d.com/downloa...PlayerFull.exe OS X, full, universal: http://webplayer.unity3d.com/downloa…-universal.dmg