As someone who has frequently shot at high ISOs, I highly recommend against it unless it is absolutely required. If it is absolutely required, then you will just have to accept the noise as Jerry said. I don't see the specific lens you were using, so hard to say if your aperture was wide open or not, however your shutter was very fast...note that with indoor or night time outdoor sports I rarely shoot anywhere near that fast - usually at 1/1000 or slightly faster based on trying to keep the ISO down as much as possible.
I would be interested to know about the lens as well...for some reason I am thinking it might be a DX lens and, if that is the case, you are only using a portion of the D810 sensor which will also tend to increase the visible noise at high ISOs...