Former San Francisco 49ers tight end Brent Jones joined KNBR this past week and said, after some discussion with sources inside the building, he finally figured out how head coach Kyle Shanahan decides who will get the majority of the workload at running back.

"What it comes down to is on Saturday night, before the game, they all go rock, paper, scissors," Jones said.

Jones, of course, was joking, but it sure seems like that's the decision-making process sometimes.

You never know who will be the team's leading rusher on any given week. It could be Raheem Mostert, Tevin Coleman, or Matt Breida. Even Jeff Wilson Jr. has been a contributor this season.

What goes into deciding when each running back will be used? Is it a particular matchup? A certain look from the defense? Or is it just a feel? Maybe it is random, as Jones humorously hinted.

Shanahan discussed the decision-making process this week with Matt Maiocco of NBC Sports Bay Area.

"We've got an idea (heading into each game)," Shanahan said. "It's something we talk about as coaches every time we game plan, every Wednesday after practice when we get there and watch together, every Thursday, every Friday. We talk about it Saturday night when I put in the openers. We talk about which guys we like more on certain ones.

"But it's kind of splitting hairs a little bit. It's not like they're all -- a huge difference. It's not like one is just really big and slow, and one's a little fast. They're all very similar. They all can run. They all can cut real well. They're all pretty similar in the pass game."

Mostert was the team's rushing leader during the final six games of the regular season, despite officially having zero starts. It was only natural to assume he would be a significant part of the rushing attack on Saturday against the Minnesota Vikings. It was Coleman, however, who received the majority of the workload last weekend.

"There are some subtle differences that we do like one more than the other on certain plays," Shanahan continued, "but it's not too hard for us because it's not like if you take one out, we're putting in a slow one. They all can run. They all do similar things that fit their skill set in our scheme.

"So, it's not too difficult for us when you've got four good ones."