Will Nault published an interesting theory on Twitter:
"I would think this relates back to the big hit he took from Doughty in Game 3. Broadcast showed him shaking off the left leg multiple times after the collision. Two-day break obviously doesn't hurt but would think you want to wrap it up Saturday and avoid a G7 for some more rest."
Here's a video of the hit:
If McDavid were to miss games, it would be a major blow to the Oilers.