Christian McCaffrey was almost unanimously the first choice in Fantasy Football this season, but the managers who selected him are biting their nails this morning after his backup, Jordan Mason, put in a great performance in Week 1 while McCaffrey was sidelined with a calf injury.

They have every reason to be concerned.

McCaffrey was a late scratch for the 49ers’ Monday night win over the Jets. He suffered a calf injury early in training camp, but early indications were that he would be good to go in Week 1. Instead, the 49ers said he wouldn’t play just over an hour before the game, and then NFL insider Adam Schefter said there’s a good chance McCaffrey will miss Week 2 as well.

It’s unclear if this is the same injury or if McCaffrey has re-injured his calf or if this is a different injury entirely. What we do know is that it’s a serious enough injury that he missed a week and could miss a second, though the fact that he hasn’t been placed on IR suggests he won’t miss more than three games.

On the field, the 49ers didn’t miss a beat as Mason, an undrafted free agent, ran for 147 yards and a TD against the Jets in Week 1. While many will view this as a one-game event, I think it could be a harbinger of relatively bad news for McCaffrey’s fantasy football managers.

Mason looked powerful and decisive when he ran the ball against the Jets, quickly opening holes and making some big runs. Part of that was because the 49ers offensive line was gobbling up the Jets’ D-line. But if he can keep running the ball like this, why would the 49ers send McCaffrey back? The answer is they won’t.

The 49ers are all about a Super Bowl this year after losing the big game last year, and knowing that the core of McCaffrey, Deebo Samuel, Trent Williams, Brandon Aiyuk, Brock Purdy and the rest won’t be together much longer. If they take that long-term view, having McCaffrey healthy in the second half of the season is far more important than having him back in the first half.

While McCaffrey will assume lead-down status in the backfield when he returns, the 49ers will likely ease him back into that role. Let’s not forget that he had 272 rushing attempts and 67 catches last year, his highest totals since his third year in the league with the Panthers. Now that he’s 28 years old, the 49ers can’t expect him to shoulder that burden again and finish the season healthy.

If Mason can take even 25% of those touches and the 49ers win, it makes sense for them to limit McCaffrey’s touches to the second half of the season. Mason’s usage (28 carries + 1 catch) and Week 1 performance indicate he can do that.

While McCaffrey is obviously a must-starter when he returns, I don’t see him repeating his performance from last year. The injury is a big reason, but there are several other circumstances that point to fantasy regression.

It may not be the news McCaffrey’s executives want to hear, but it appears this is the reality.