Marner also being injured doesn't mean their regular season play was impacted exactly the same. Mikko also followed up the season with 21 points in 15 playoff games.
And, why do you think the stars in the West are underperforming? Do you think that maybe it's because the teams they are facing are playing really well defensively? Or because they have to face guys like MAF, Gibson, Quick/Campbell, Keumper/Raanta, Binnington, Kahkonen and Grubauer in net? The only guy in the West who hasn't put up a good SV% is Jones, but then you have Couture, Burns, Karlsson, Vlasic, etc. to deal with.
If Rantanen doesn't get a pass for struggling through an injury plagued season, why does Marner get a pass for struggling in the playoffs?