Niners placing Christian McCaffrey (calf/Achilles) on injured reserve; RB to miss at least four games

McCaffrey sat out most of training camp and did not play in the preseason due to a calf strain that head coach Kyle Shanahan announced on Aug. 6.

The threat level seemed low, though, as Shanahan said a few weeks later he wasn’t concerned with McCaffrey’s readiness while dealing with the injury. Bigger issues seemed to be on the horizon, namely left tackle Trent Williams holding out and wide receiver Brandon Aiyuk holding in due to contract disputes.

But those standoffs both came to an end ahead of Week 1, and Williams and Aiyuk suited up for the team’s 32-19 victory over the New York Jets on Monday Night Football.

McCaffrey, surprisingly, did not, and now he won’t for quite some time.

Jordan Mason served as San Francisco’s RB1 in his stead, exploding for 152 yards and a score on 29 touches. It was a stupendous prime-time performance that bodes well for the 49ers withstanding a stretch without their most dangerous weapon, but there’s still no replacing everything the versatile McCaffrey, a two-time All-Pro and one of the finest pass-catching backs in the NFL, brings to the table.

It’ll likely take Deebo Samuel contributing more time in the backfield as he did on Monday to help fill the receiving void there, plus a greater sprinkling of backups Isaac Guerendo and Patrick Taylor (three offensive snaps combined in Week 1) to keep Mason fresh in his potentially newfound workhorse role.

The 49ers play the Minnesota Vikings, Los Angeles Rams, New England Patriots and Arizona Cardinals over their next four games. If CMC spends the minimum amount of time on IR, he could return for a Thursday night showdown against the Seattle Seahawks on Oct. 10.

San Francisco’s two games scheduled between that contest and a Week 9 bye take place at home against the Kansas City Chiefs and Dallas Cowboys.