I work at a hospital and actually asked a few of the people I work with (2 of them actual doctors), and they say if it's a Grade 2 LCL sprain, he's done not just for this series, but the whole postseason. A tear isn't going to just heal up completely in a month, and it'll likely be 6-8 weeks.
Maybe his injury is between a Grade 1 and Grade 2 (if that's even possible), but even then that doesn't sound good for his chances of playing this series. Up until the gap between Games 6-7, the games are every other day this series. Not like they have 2-3 days off in between games where he could rest up and potentially return.