I'm undecided. Lots of guys can look good for 3 games with good blocking and a positive game flow. If you look at his splits, he had 27 carries @ 6.0 ypc while leading big and added another 7 carries @ 8.9 ypc while trailing big. Everything in the middle (40 carries) was ho-hum. Granted, looking at splits for a 3 game sample is about as meaningless as looking at a 3 game sample for a rookie... but I'm just saying, things broke right for him in those 3 games so I'm not crowning him an elite-level talent yet. It would not surprise me at all if he was actually more of an Eddie Lacy or Thomas Rawls type of talent - both guys who have put up some elite looking 3 game stretches. Again, I'm not predicting that outcome, just saying it isn't outside the realm of realistic outcomes.All comes down to how good you believe Cook is. I think he's an elite-level talent. I don't believe McKinnon is anywhere close to him in terms of talent. But as we know in fantasy, talent is only part of the equation. Opportunity is vital too. McKinnon clearly has an opportunity now but I'd caution against viewing him as a 20+ per game RB like Cook was.
Something to consider - he played 78% and 73% of the snaps in weeks 1 and 3, games in which they were leading for the vast majority of the time. He was only at 56% in week 2 and his utilization was cut in half compared to weeks 1 and 3 (so he wasn't actually guaranteed a massive workload like some are implying). McKinnon will probably be the opposite of this. I expect they'll use Murray to run out the clock and McKinnon when they're in come from behind mode. So I agree McKinnon isn't going to inherit Cook's role, but in PPR leagues he should hold quite a bit of value (he was barely behind Cook in targets through 3 weeks despite the snap difference).