Week 1 started off shockingly for the San Francisco 49ers.

Star running back Christian McCaffrey was a last-minute scratch against the New York Jets. His month-long calf/Achilles injury was too much to overcome. It was shocking to see, considering how determined he was to play.

“The same stuff that’s been bothering him all week,” Kyle Shanahan said of the decision to sit McCaffrey out. “There was a little too much today, a game-time decision. He came in, just talked to him about it, it was still there. I thought it would be smart to sit him out and I’m glad we did.”

It was definitely a smart decision to sideline McCaffrey. An Achilles injury is no joke, no matter how mild. Sidelining McCaffrey is also easy when the 49ers have a top backup in Jordan Mason. And boy, was he phenomenal against the Jets, carrying 28 times for 147 yards and a score.

The 49ers are expected to rest McCaffrey against the Minnesota Vikings in Week 2. It’s best to err on the side of caution with McCaffrey. The time he was inactive against the Jets indicated his injury was worse than he let on.

McCaffrey is an extremely tough player. If his injury was mild, he would have played. But the fact that he couldn’t play shows that he is dealing with a tough injury. Also, his calf/Achilles tendon isn’t going to get drastically better in less than a week.

Resting him against the Vikings, an average opponent at best, is a smart move. The 49ers offense didn’t fluctuate much with Mason as the starter. Mason has proven that the offense can stay at a high level with him as the starter. His performance against the Jets should make it an easy decision for the 49ers to make regarding McCaffrey’s status.

But Shanahan doesn’t see it that way.

“Not really. We’ve always, we think very highly of JP. When he’s been in those situations, that’s what he’s always done,” Shanahan said. “You always want Christian on the field. What he brings to the run game, and also what he brings to the pass game. It’s great to have Christian. But it’s at the cost of losing him for more games.”

It makes sense that Shanahan wants his best offensive player back. If he’s healthy and ready, the 49ers will let him play. But why take that risk if it’s unnecessary? They don’t necessarily need him back. The 49ers have a good running back in Mason to keep them dominant.

Sitting McCaffrey out another week to rest him isn’t as damaging as letting him play. The 49ers have to think about the entire season here. His calf/Achilles is an issue that’s been going on since late last year. Take the slow approach with him or risk missing him longer.

The decision here is easy. Put him against the Vikings and let Mason continue to flourish. His place will be there once he is fully fit.