The San Francisco 49ers held a light practice on Saturday and nearly got to the end without any injuries. On the last play during 11-on-11 drills, running back Jerick McKinnon went down with a torn ACL. The severity of the injury was confirmed on Saturday after an MRI was performed on McKinnon's right knee.
"He made a cut on air," head coach Kyle Shanahan told reporters via a conference call on Saturday. "It was the last play of practice. Made a cut on air. No one was around him. Just went down. It looked awkward."
The non-contact injury occurred shortly before the 49ers finalized their 53-man roster. The injury leaves the team with running backs Matt Breida, who is returning from a separated shoulder, Raheem Mostert, and newcomer Alfred Morris, who was signed on August 14.
Breida and Morris are now expected to share the workload on offense this season.
McKinnon, who was returning from a calf strain sustained on August 12, was expected to be the 49ers' featured back when they opened the season on September 9 against the Minnesota Vikings. It would have been a homecoming for the running back. The Vikings made McKinnon a third-round draft pick in 2014 and he played each of his four NFL seasons there.
McKinnon registered 1,918 career yards on 474 carries with seven touchdowns. He also added 94 receptions for 676 yards with four touchdown catches since 2016.
The 49ers also officially placed safety Marcell Harris on injured reserve. To take the two roster spots, the team signed defensive back Antone Exum Jr. and offensive lineman Matt Tobin.
San Francisco selected Harris out of Florida in the sixth-round of April's draft. He had a slow start with the Gators because he was recovering from a knee injury suffered in high school. Harris had a break-out season as a junior in 2016 when he registered 73 combined tackles, four for a loss, a forced fumble, a fumble recovery, a sack, and scored a touchdown on defense. He did not play during his senior season after suffering a torn Achilles last summer.