Christian McCaffrey ruled out ...

Christian McCaffrey will be out for the San Francisco 49ers' Week 2 game against the Minnesota Vikings and potentially longer.

The Niners ruled out the Pro Bowl running back Friday, with Niners head coach Kyle Shanahan telling reporters the team is considering an injured reserve stint due to his calf/Achilles injury:

"It's something we're considering now. [Thursday] was his worst day. It's on and off, but with yesterday having the most pain, something we're going to be discussing the next 24 hours."

An IR stint would keep McCaffrey out until at least Week 6.

McCaffrey was a surprise inactive for the Niners' opener against the New York Jets on Monday, as the star was only considered questionable after a week of limited practice. His issues were later revealed to include Achilles tendinitis, hence why the team would exercise caution.

McCaffrey being inactive might not have been a surprise to everyone, though, as backup running back Jordan Mason told reporters he found out he was starting around Friday night. Shanahan denied anyone told Mason he was the starter that early. The NFL looked into the matter — the league takes a dim view of teams hiding injury info — and announced Friday it had cleared the team:

“We have looked into the 49ers’ reporting of the playing status of Christian McCaffrey for the team’s Monday night game against the New York Jets. We have found no evidence of a violation of the league’s Injury Report Policy in this matter.”

This week, McCaffrey was limited in practice both Wednesday and Thursday, then a non-participant Friday.

The good news for the Niners is Mason looked excellent in their Week 1 win over the New York Jets, accruing 147 rushing yards and a touchdown on 28 attempts. No other running back received a non-garbage time snap.

The San Francisco offense as a whole barely seemed to miss a beat, gaining 401 total yards and 32 points against a Jets defense expected to be one of the better units in the NFL.

With McCaffrey out, the Niners are still a 4.5-point favorite (-225 on the money line) at BetMGM over the Vikings, who posted a 28-6 win over the moribund New York Giants in Week 1.