San Francisco 49ers running back Elijah Mitchell will spend at least the next six weeks on the sidelines after suffering his second MCL sprain of the season in Sunday's win against the New Orleans Saints.

It is the same injury he suffered in Week 1, and in that instance he did not return until Week 10, proceeding to contribute in three consecutive wins before bad luck struck again.

A sixth-round pick in last year's NFL Draft, Mitchell burst onto the scene with 1,100 yards from scrimmage as a rookie, but following his injury to begin this season, the 49ers made the decision to invest further in the running back position.

Their trade for former Carolina Panthers superstar Christian McCaffrey insulates the 49ers from the crushing blow of this injury, as it will result in an increased workload for the two-time All-Pro.

Niners head coach Kyle Shanahan said he felt for the 24-year-old after the news of his impending stint on the sidelines.

"It wasn't the news we were looking for," he told reporters. "He's pretty disappointed. 

"Everyone knows how good Elijah has been, how hard he worked to get back from his last one, how good he's been playing since he came back, and to kind of be right back there, I know he was real down on it. 

"It's unfortunate for him. He's just had some real bad luck."

He added: "He knows what's ahead of him. He's just going to have about six weeks of frustration, but hopefully we can do our job here so when he comes back, we're still playing."

There are six weeks remaining in the regular season, and with a 7-4 record, the 49ers are a strong contender for a deep playoff run.