Monday evening brought a bit of a surprise development as the San Francisco 49ers declared running back Christian McCaffrey inactive for their season opener against the New York Jets on Monday Night Football.

McCaffrey has been dealing with Achilles and calf injuries. The news is not shocking due to limited practices, but McCaffrey said he expected to play in Week 1. Instead, he will be sidelined and the 49ers will start Jordan Mason in the backfield against the Jets. They will also lean on Isaac Guerendo and Patrick Taylor, Jr., but Mason is the starter heading into kickoff.

What this means for fantasy football and the waiver wire

Game update: Jordan Mason was a beast against the Jets. He rushed 28 times for 147 yards and a touchdown. It was his most rushing attempts since high school and only Deebo Samuel got any other significant rushing work. Isaac Guerendo and Patrick Taylor, Jr. did not get any touches as this was all Mason. We’ll see what we hear over the next 24 hours before you have to make a decision. Given his performance, there’s no reason for the 49ers to rush back McCaffrey, so he’s still a solid waiver value. And he is at worst a great handcuff.

If you were relying on McCaffrey as your top pick, you are left scrambling on Monday night. Mason is rostered in 39% of leagues at Yahoo!, so there’s a chance you could grab him. Guerendo is rostered in 1% of leagues and Taylor is available in virtually all leagues. On the Jets side of things, Breece Hall won’t be available. His backup, Braelon Allen, is only rostered in 12% of leagues. You’d be better served rolling the dice on any of the 49ers options.

Coming out of Week 1, it’s unclear what any of this means. McCaffrey might have just needed one more week, but we’ll keep an eye on Kyle Shanahan’s post-game comments to get a better handle on what this means moving forward. If there isn’t clarity, Mason will be a popular waivers pick. Of course, given how Shanahan has used non-McCaffrey running backs in the past, Guerendo and Taylor could be worth stashing as lottery tickets.

We’ll update this article with how Mason and the rest of the 49ers running backs look on Monday evening against the Jets.