The other running backs on the roster rallied around their injured teammate as they prepared to carry the load. Raheem Mostert spoke with Damon Bruce on 95.7 The Game on Wednesday and shared the message the running backs had for McKinnon after the injury.
"Don't worry about it, Jet," Mostert and the group told him. "You get back healthy. You get straight. When it comes go time next year, we know you're going to be ready just like how you know we were going to be ready when anything happens."
Head coach Kyle Shanahan and the 49ers had no choice but to press forward without McKinnon. The bad situation got worse when franchise quarterback Jimmy Garoppolo went down, also with a torn ACL, during a Week 3 visit to Arrowhead Stadium.
Matt Breida stepped up when McKinnon went down but has been dealing with injuries himself. Mostert, a key special teams contributor in his three previous NFL seasons, has been helping to fill in. His 157 rushing yards over the past three games already marks a career-high.
Mostert has averaged 7.7 yards per rushing attempt over the past two games, which would easily rank tops among running backs this season if not for the limited sample size. He and teammate C.J. Beathard, who is starting in place of Garoppolo, are trying to fill the shoes of the two offensive players Shanahan hoped to build his offense around this season and beyond.
Shanahan sounded hopeful on Wednesday that Breida would be healthy enough to play in the 49ers' Week 8 rematch against the Arizona Cardinals. If not, Mostert feels ready to do whatever is asked of him.
McKinnon and Garoppolo may not be out on the field on Sundays, but their presence is felt and appreciated in team meetings. Whether it be Breida, Mostert, or Beathard, the 49ers backups thrust into more playing time know they can depend on the two injured players for knowledge and support. McKinnon and Garoppolo have been in the building. They are around.
Garoppolo is three weeks removed from his knee surgery. He rejoined his teammates last week while McKinnon has been there for some time.
"C.J. can pick Jimmy's brain and see what he would do in a certain situation," Mostert explained. "The same thing for me and Jet. I'll ask Jet after a game, 'Hey man, what did you think about this run?' He'll be like, 'Aw man, if you would have just went to the left a little bit more, you probably would have took it to the house.'
"That communication, that's the type of brotherhood that we have in the locker room. We see them as fallen soldiers right now, but at the end of the day, they're still our brother, and we're still going to look after each other, and ask each other questions, and pick each other's brains."
Both Garoppolo and McKinnon, who have become rehab brothers following their injuries, are expected to be ready by next season. Until then, the 49ers' current season relies on players like Mostert, Breida, and Beathard to step up and help turn things around. That starts on Sunday when the team tries to earn its secone win of the year.
You can listen to the entire conversation with Mostert below.