Most of the speculation about the injury so far has stemmed from his poor play (frankly, he's been poor for around 3 months now, so not sure why some people are surprised he's not been great this series). But his deployment (as you mention, he does the PK), his faceoffs (he's taken 49 faceoffs in 5 games, which is a similar pace to his 799 in 82 games over this season), and the fact that he played Game 82 when some other core players did not, would indicate that he's not significantly hurt.
I guess we'll only know for sure afterwards.