Prior to their second game of the season against the Minnesota Vikings on Sunday, the San Francisco 49ers officially placed All-Pro running back Christian McCaffrey on the injured reserve. McCaffrey will now miss at least the next four games as he continues to heal from a calf/Achilles injury that kept him out from most of training camp and all of the preseason.

With shifting McCaffrey to the injured reserve, the 49ers will have a new opening on their 53-man roster. As of Saturday, the 49ers have yet to fill their opening on the official 53.

After announcing McCaffrey to the IR, the 49ers also announced the elevation of safety Tracy Walker from the practice squad.

Via @49ers on Twitter:

Walker III will provide depth in the secondary with fellow safety Talanoa Hufanga listed as doubtful. Walker III was elevated from the practice squad during the season-opener against the New York Jets, but he did not play a single snap.

With McCaffrey on the IR, breakout running back Jordan Mason will continue to serve as the starter next to Brock Purdy in the 49ers backfield. Mason rumbled for 147 yards and a touchdown in his first start against the Jets on Monday.

The 49ers are set to meet Sam Darnold, Justin Jefferson and the 49ers on Sunday in Minnesota at 10 a.m. PT.

This post originally appeared on Niners Wire! Follow us on Facebook and Twitter!

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This article originally appeared on Niners Wire: 49ers won’t replace Christian McCaffrey on roster yet