Why the Jaguars could expose this weakness in the 49ers defense

This will be a new challenge for San Francisco.

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The San Francisco 49ers' Week 4 matchup with the Jacksonville Jaguars will be a great test to see just how good the run defense is. The unit has held up so far, but Jacksonville will be the best group that they have faced. 

The San Francisco 49ers will face a tough rushing attack against the Jacksonville Jaguars

In Week 1, they took on a Seattle Seahawks team that had a new quarterback and play-caller. They also appear to be shuffling their running backs. In Week 2, they faced a new head coach who was calling plays and a quarterback who had yet to win in the NFL. They also entered the game with questions along the line. The 49ers faced the Cardinals in Week 3, but Arizona had already struggled to run the ball, and then they lost James Conner. 

In all, they have faced the 22nd, 27th, and 21st best rushing attacks in the NFL according to success rate, respectively. Now, San Francisco faces the Jaguars, who come into Week 4 with the ninth-best rushing attack in this metric. 

To be fair to San Francisco, some of the success rate numbers are so low because of their defense. On top of that, Jacksonville faced Carolina and Cincinnati, who have had trouble against the run. Between the pass and the run, Houston is better against the pass as well. 

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So, while this will be a test for the 49ers, it will also be a step up for Jacksonville. Still, the Jaguars hired Liam Coen to be their head coach to inspire the run game. He did just that in his first year as the Tampa Bay Buccaneers playcaller. It led to a breakout by Bucky Irving and a new job for Coen. 

The Jaguars brought in Robert Hainsey and Patrick Mekari to start this offseason, and the change in scheme appears to have reinvigorated Travis Etienne. They have also been getting more from their rookie Bayshul Tuten in the last two weeks. 

San Francisco has been figuring things out on offense due to so many injuries, and their defense has been able to lead them through. However, with Nick Bosa injured and facing a hot Jaguars rushing attack, it may be time for the defense to call on the offense for some help. 

It will be interesting to see if Jacksonville continues to run the ball well, or if we see the 49ers' flaws on defense start to show.