The 49ers were looking for a source of surprise in a time of desperate need.

San Francisco picked up running back Israel Abanikanda on a waiver claim from the Jets following a series of injuries in their backfield.

In the team’s announcement of the transaction, the 49ers said they had placed Christian McCaffrey back on injured reserve due to a PCL sprain he suffered in Sunday night’s loss to the Bills.

McCaffrey is expected to be out about six weeks, so the injury will likely spell the end of his regular season.

Making matters worse, McCaffrey’s backup Jordan Mason suffered a severe ankle sprain, and coach Kyle Shanahan said Monday that Mason is also expected to be placed on IR, meaning he will miss at least four games.

The two injuries – plus Elijah Mitchell, who has been on IR (hamstring) since August – left only Isaac Guerendo as the only healthy running back on the 49ers’ active roster.

Abanikanda was a fifth-round pick from Pittsburgh in 2023 and played six regular-season games for the Jets last season.

The Brooklyn native rushed for 70 yards on 22 attempts and caught seven balls for 43 yards.

The 22-year-old Abanikanda has not played in any of the Jets’ 12 games this year and was released by the team on Monday.

The 49ers entered this season with championship aspirations after narrowly falling short of the Chiefs in a thrilling 2024 Super Bowl.

But with injuries piling up at key positions across the field, the 49ers are now 5-7, with NFL.com giving them just an eight percent chance of reaching the postseason.

San Francisco hosts the Bears on Sunday, hoping to keep their slim NFC hopes alive.