Oh I agree with what you're saying, but I don't see what it's got to do with PotS. At least with Murray, he's got replacements (Hemed, eventually Baldock and now, fortunately, Ulloa and Locadia), I'm not so sure you could say the same with Gross, but that doesn't qualify him to be PotS.
For me, it's between Gross, Dunk, Murray and Ryan. Izquierdo has been in form of late and arguably our best player in that period, but apart from West Ham away his performances during 2017 weren't up to much. I don't buy the argument that Gross shouldn't get it because he's been inconsistent...