The grade of the strain is all subjective. You could have 10 doctors view it and maybe they split 50/50 on the grade. Bottom line will be how KP's body responds to it. If it were grade X it doesn't mean he will miss Y days no more or no less.
Before the season started, I had high hopes for this team, but you never know until you see them actually play together. After the first 20 games or so, I was convinced they'd be a top 3 title contender, and a lot of that hinged on KP staying healthy. All in all, did a pretty good job staying healthy until later in the season. Not sure if he really had something or they were just being more cautious. But this injury is pretty scary. I see these "worst case" posts about him coming back at some later round. Worst case really is not coming back for this playoffs. Let's hope for the best.