49ers' Christian McCaffrey to be placed on IR after suffering PCL injury

San Francisco 49ers running back Christian McCaffrey's season might be over.

The star running back will be placed on injured reserve after suffering a PCL injury in his left knee, 49ers coach Kyle Shanahan told reporters on Monday. With the injured reserve placement, McCaffrey will miss at least four games, though Shanahan said the injury would take six weeks of recovery. San Francisco only has five regular-season games remaining on its schedule.

McCaffrey suffered the injury in the second quarter of Sunday's 35-10 loss against the Buffalo Bills. He stepped awkwardly on a sweep to the left on a snow-slicked field. The All-Pro went down almost immediately for a 5-yard loss. He went to the sideline and was examined in the medical tent. He was initially ruled as questionable to return before being ruled out. 

Additionally, 49ers backup running back Jordan Mason will be placed on injured reserve due to a high-ankle sprain. As a result, rookie Isaac Guerendo will become the team's new lead running back. 

The outing was McCaffrey's fourth this season after the 2023 offensive player of the year missed the Niners' first eight games with Achilles tendinitis. His 19-yard run in the first quarter was his longest of the season, and he had seven carries for 53 yards and two catches for 14 yards before getting hurt.

In four games, McCaffrey has totaled 50 carries for 202 yards, along with 15 catches for 146 yards. He has not scored a touchdown this season.

Mason took over as the 49ers' featured back when McCaffrey left and finished with 13 carries for 78 yards. Guerendo also ran the ball four times for 19 yards and a touchdown.

The Associated Press contributed to this report.

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