The 49ers signed quarterback Adrian Martinez to their active roster from the practice squad on Thursday, per Matt Maiocco of NBC Sports Bay Area.

For the third time in four weeks, Martinez will serve as the backup to Mac Jones, who is starting once again in place of an injured Brock Purdy.

Martinez was elevated from the practice squad in Weeks 2 and 3, and the 49ers had the option to use up his third and final elevation for Thursday’s game. Instead, they signed him to the 53-man roster, which will ensure he is available to play as long as Purdy is sidelined after his recent setback.

Jones played every snap in his two starts, winning both games with a total of 563 passing yards and four touchdowns. Turnovers are somewhat of a concern – Jones threw one interception and fumbled twice (one lost) – but he would have to implode for the 49ers to put in Martinez for his NFL debut. Instead, the team will be hoping that Martinez only takes the field if they have built up a massive lead.

A former starter at Nebraska, Martinez spent his senior year at Kansas State, where he tossed six touchdowns vs. one interception. He also had a standout performance while running the ball, collecting another 627 yards and 10 touchdowns. He joined the Lions after going undrafted in 2023, and he later won UFL MVP before winning the league championship with the Birmingham Stallions. He spent the 2024 season on the Jets practice squad and was among the team’s final cuts following the 2025 preseason. He caught on with the 49ers practice squad in late August.

The 49ers offense will also be without wide receivers Ricky Pearsall and Jauan Jennings on Thursday night, giving them an uphill battle against a strong Rams defense on a short week.

Joining Martinez from the practice squad will be defensive end Trevis Gipson and wide receiver Malik Turner, who have been called up as standard gameday practice squad elevations. To make room for Martinez on the 53-man roster, defensive tackle Jordan Jefferson was waived, and to fill Martinez’s open spot on the practice squad, the team signed cornerback Derrick Canteen.