The 49ers on Thursday promoted No. 3 quarterback Adrian Martinez to a spot on the team’s 53-man roster.

Martinez will serve as the backup quarterback when the 49ers face the Los Angeles Rams on Thursday night at SoFi Stadium.

Mac Jones will start for the third time this season, as the 49ers declared Brock Purdy out for the game with a toe injury.

The 49ers released defensive lineman Jordan Jefferson to make room on the 53-man roster for Martinez.

The 49ers elevated wide receiver Malik Turner and defensive end Trevis Gipson from the practice squad to play against the Rams.

Turner will be one of five receivers in uniform for the 49ers. Ricky Pearsall (knee) and Jauan Jennings (ankle, ribs ) will not be active due to injuries.

The 49ers also re-signed cornerback Derrick Canteen

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