Do 49ers have an emergency plan at QB if Brock Purdy, Mac Jones are out?

The San Francisco 49ers may have the NFL's worst injury luck at the most important position.

49ers starting QB Brock Purdy hasn't played since Week 1 because of left shoulder/toe issues. And now backup Mac Jones is battling a knee injury he reaggravated in a Week 3 win over the Arizona Cardinals (2-1).

On Wednesday, 49ers head coach Kyle Shanahan said both QBs will be limited during practice. He added Purdy is healthier than he was in Week 3 but didn't commit to him playing in Sunday's home game against the Jacksonville Jaguars (2-1). Who will San Francisco (3-0) start if both signal-callers are out? 

49ers' replacement for Purdy and Jones isn't ideal

The 49ers would elevate backup QB Adrian Martinez from the practice squad if Purdy or Jones can't play. The Nebraska/Kansas State product starred for the Birmingham Stallions in the UFL during the 2024 season. That year, he won both the league MVP and the UFL Championship MVP awards. 

However, Martinez — who has yet to attempt a pass in a regular-season game — has struggled to latch on in the NFL. The Detroit Lions and New York Jets have waived him. The Niners signed him to their practice squad in late August.

"No. Brock will get some, Mac should still get some, but they're not going to get their full amount," Shanahan said when asked if Martinez would take all the first-team reps Wednesday. "He'll get a little more, Adrian."

The best-case scenario for the Niners would be the one-time Pro Bowler Purdy returning from injury. In a 17-13 Week 1 win over the Seattle Seahawks, he finished 26-of-35 passing for 277 yards, two touchdowns and two interceptions. 

Jones, meanwhile, has looked serviceable for the 49ers. He's 2-0 in two starts and has tossed four TD passes.

The 49ers better hope Jones or Purdy is healthy for Sunday. The inexperienced Martinez may not be ready to carry them to victory.