49ers 'nervous' after RB Jerrick McKinnon goes down with injury in practice

Report: 49ers RB Jerick McKinnon out for season after MRI reveals torn ACL

The San Francisco 49ers are holding their breath after starting running back Jerrick McKinnon suffered an injury in practice on Saturday.

McKinnon reportedly went down on the last play of a team workout while making a cut, without contact:

Per NFL Network reporters Ian Rapoport and Mike Garafolo, it “appeared to be a concerning injury.”

Niners head coach Kyle Shanahan all but confirmed the concerning nature of the injury, telling reporters after practice: “We’re nervous about it, that’s for sure.”

The extent of the injury, though, is not yet known.

This story will be updated shortly.