McKinnon could be in line for primary backup duties behind Raheem Mostert if Tevin Coleman (health concern) is held out due to poor air conditions against the Cardinals on Sunday.
Coleman has sickle cell trait, which puts him at increased risk for contracting breathing problems in unhealthy air conditions like the current one in Santa Clara. The air quality index (AQI) sat between 150-200 Friday at Levi's Stadium, which is extremely poor for even a healthy human. Assuming the game doesn't get postponed, McKinnon would stand to benefit the most if Coleman is held out of the contest. Head coach Kyle Shanahan routinely uses a tandem backfield approach, so whichever player backs up Raheem Mostert should see touches in the low double-digits. McKinnon hasn't logged an official snap since signing a big free-agent contract with San Francisco in 2018, but the 28-year-old could flourish in Shanahan's zone-run scheme that utilizes speedy backs who can catch. Expect a final decision on Coleman's status between now and kickoff Sunday.