Mac Jones to Start Week 2 for 49ers as Brock Purdy Injury Timeline Revealed

With Brock Purdy sidelined for multiple weeks, the San Francisco 49ers are forced to turn to veteran backup Mac Jones.

San Francisco 49ers quarterback Brock Purdy (13) looks on during warmups before the game against the Seattle Seahawks at Lumen Field. | Joe Nicholson-Imagn Images

After missing the playoffs in 2024, the 49ers hoped the return of Christian McCaffrey, paired with the new contract ($265 million) for Brock Purdy, would lead to a deep playoff run this year. After Week 1, San Francisco already has two massive dings in their starting lineup.

The 49ers placed George Kittle on injured reserve earlier this week with a bad hamstring issue, leaving massive weakness for their passing game at tight end. 

Brock Purdy Goes Down

Purdy came out of last week’s game with a turf toe injury, giving him a questionable tag for his matchup on the road against the Saints. Unfortunately for San Francisco fans, he has been downgraded to doubtful, with a new update of him missing two to five weeks. If the 49ers place him on the IR, they will be in survival mode at quarterback for at least a month.

49ers QB Brock Purdy will miss 2-5 weeks with a form of turf toe. (via @rapsheet) pic.twitter.com/CcuyQngF6H

— NFL (@NFL) September 11, 2025

The next man up is Mac Jones, who brings a reasonable completion rate (65.9%) over four seasons in the NFL. Unfortunately, he has a 4-14 record over his last 18 starts after showing winning promise (10-7) in his rookie season, after New England drafted him 15th overall in 2021. 

Mac Jones Fantasy Football Outlook

San Francisco 49ers quarterback Mac Jones (10) drops back to pass in the first quarter against the Denver Broncos at Levi's Stadium. | David Gonzales-Imagn Images

Over the past three seasons, Jones has almost as many interceptions (31) as touchdown passes (32) while gaining only 6.5 yards per pass attempt, an area Brock Purdy (8.9) has excelled at in the 49ers’ offense. His sack percentage (6.17) isn’t that far off from Purdy's (6.04), but his QBR rating (84.9) is miles away from San Fran’s star quarterback (104.5).

The best-selling point for Jones could be the development of Brian Thomas over his last seven games (50/675/5 on 77 targets – 13.5 YPC) in 2024.

Fantasy Football Impact Of Brock Purdy Injury

As for the 49ers, their scoring upside takes a significant hit with Purdy out of the lineup, which doesn’t even include how defenses can attack Christian McCaffrey and San Francisco’s wide receivers with George Kittle injured. 

From a betting line perspective, the 49ers opened this week as seven-point favorites on the road with an over/under of 43.5. The post Brock Purdy injury line is set at San Francisco at -3 in New Orleans, with a drop of three points in the game total.

As for the 49ers’ offense, Jones is more than capable of being a game manager, especially when playing from the lead. He does a decent job in the deep passing game, while tending to get the ball out quickly when under duress. The downside of this leads to many more short completions, a win for Christian McCaffrey in catches, and fewer points scored.

I expect the tight end position to offer no fantasy value in San Francisco until Kittle returns. At best, Jones is a league-average passer, delivering about one passing score per week, thus lowering the overall production of his top two wideouts. Ricky Pearsall has a better chance of holding value due to his ability to stretch the field and work the short passing zones. I can’t trust Jauan Jennings due to his missed time this summer with calf issue and more missed practice time this week with a shoulder injury.