The 49ers received some bad news surrounding their top running back as they made final cuts on Saturday.
Jerick McKinnon, who was expected to be ready to go this week after suffering a calf strain during practice Aug. 12, suffered a knee injury on Saturday and was set to undergo an MRI the same day. The team is fearing it could be serious.
“He made a cut on air ... no one was around him, he went down, looked awkward,” Kyle Shanahan said on a conference call. “We’re nervous about it, that’s for sure.”
Shanahan indicated the team hasn’t ruled out an ACL tear, which would presumably end McKinnon’s season. He signed a four-year, $30 million contract in March to be the team’s primary running back replacing Carlos Hyde.
“Anytime I watch someone feel their knee, there’s always that concern,” Shanahan said. “But I felt that way before, and it hasn’t been. ... We hope that we’re wrong.”
The 49ers held a practice on Saturday after determining their 53-man roster. It was McKinnon’s first practice with the team in 11-on-11 drills since straining his calf. He had been going through extensive workouts before each of the last two preseason games to gear up for his return to Minnesota Week 1 to play his former team.
San Francisco was forced to put McKinnon on the 53-man roster without knowing the severity of the injury ahead of Saturday’s 1 p.m. deadline. If he’s forced to injured reserve, it would open up a roster spot elsewhere and possibly allow the team to bring back recently cut running backs Joe Williams, Jeremy McNichols or undrafted rookie Jeff Wilson Jr.
“It was unusual, the timing of it,” Shanahan said. “We don’t know for sure until we get an MRI. He’s got to be a part of our 53. And if we get a bad MRI, tomorrow, obviously he’ll have to go on (injured reserve). So that’s why everything is very fluid. Because that affects our 53 and our practice squad and everything.”
The 49ers signed Alfred Morris last month to provide depth and an insurance policy while dealing with injuries to McKinnon and his backup Matt Breida, who suffered a separated shoulder in the preseason opener.
Breida was also on the practice field Saturday and is expected to be ready against the Vikings.
Morris impressed in his San Francisco debut in the third exhibition contest, rushing for 84 yards on 17 carries (4.9 average). The team’s third running back is Raheem Mostert, who made the team primarily for his work on special teams.
Editor’s note: This story has been updated to clarify the timing of the MRI.