The 49ers face a daunting test Thursday night in the form of Cardinals rookie quarterback Kyler Murray. Facing the dynamic Heisman Trophy winner on short rest could spell trouble, even for a dominant defense. 

"[It's] a challenge," 49ers defensive coordinator Robert Saleh said Tuesday of facing a new-look team for the first time on a short week. "This is not a simple offense. They've got a lot of cool designed plays and they do a lot of things. Having the quarterback in the run game is a problem. So, on a short week, you're actually more comfortable going against a system that's been in place for a while because you have a good feel for what's going to happen."

But San Francisco's defense has been so ruthless on quarterbacks this season, it might not matter who is behind center or how much time the 49ers have to prepare. Look no further than fantasy football to show how much trouble this group has given opposing QBs. 

If you started a QB against the 49ers' defense, you should just take the loss and move on to the next week. Here's your proof. 

That's right, quarterbacks have averaged 2.9 fantasy points against the 49ers in the last four games. Pro Football Focus' Daniel Kelley is using PFF's scoring system, and says the number could be even lower for other outlets.

 

The 49ers defense has five interceptions over that span and has forced two fumbles from the QB. The last four quarterbacks they have faced -- Baker Mayfield, Jared Goff, Case Keenum and Kyle Allen -- have averaged just 103 passing yards per game. Allen's 158 yards top the group, but he was intercepted three times. 

[RELATED: Murray calls Nick Bosa 'a freak' before 49ers game]

San Francisco's defense leads the NFL in yards allowed per game (224.4) and passing yards allowed per game (128.7). The 49ers (11.0) are behind only the Patriots (7.6) in points allowed per game. 

Thursday night will be a new challenge for the 49ers when they go up against Murray and the Cardinals. The same goes for the rookie QB, too. 

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