San Francisco 49ers: Run defense should thrive still without Arik Armstead

The San Francisco 49ers will be without Arik Armstead for four to six weeks, but should still be a force when it comes to defending the run.

The San Francisco 49ers defense may not be the force it once was, but one area in which this young group is underrated is in stopping the run. San Francisco is giving up 112.8 rushing yards per game, good for No. 18 in the league, a substantial improvement from when they ranked last in the league in the same category in 2016.

Football Outsiders ranks the 49ers at No. 13 in the NFL in run defense DVOA and a primary reason for their success in that regard has been because of the talent they possess on the defensive line. Having spent first-round picks on defensive linemen in three successive drafts, the Niners are seeing the dividends of those investments.

The 49ers are allowing opposing running backs just 3.6 yards per carry. In addition, per Football Outsiders, they have allowed a power success rate of 58 percent, meaning 42 percent of third and fourth down runs with two yards or less to go that they have faced have not resulted in a first down. Only 10 teams in the league are better than San Francisco in that category.

More from NFL Spin Zone

• Dallas Cowboys made the trade everyone else should have made
• Pittsburgh Steelers rookie sleeper everyone should be talking about
• Anthony Richardson putting jaw-dropping talent on display immediately
• Denver Broncos’ stud wide receiver might be out for a while
• Washington Commanders: Three takeaways from win over Ravens

Football Outsiders also has the 49ers ranked at No. 8 in the NFL at stuffing running backs at or behind the line of scrimmage. Justis Mosqueda of the Setting The Edge podcast rates San Francisco’s tackle for loss value as 5.5 percent better than the NFL average.

All these numbers make very pleasant reading for the 49ers and defensive coordinator Robert Saleh, and are a direct result of the play produced by their three first-rounders, DeForest Buckner, Solomon Thomas and Arik Armstead. Buckner has caused havoc on the inside for opposing offensive lines and is graded by Pro Football Focus Edge as the second-best interior defensive lineman in the league, with only Aaron Donald ahead of him.

He has four tackles for loss and this year’s third overall pick Thomas is level with him through six games, the former Stanford star logging nine run stops in the last five games, per PFF on Twitter, trailing only Joey Bosa, Emmanuel Ogbah and Calais Campbell in that period. That duo will have an extra burden on their shoulders now, with Armstead ruled out for four to six weeks following surgery on a broken hand.

Armstead’s stats may not be as impressive as those of Buckner and Thomas, but his impact on the field is undoubted. He uses his frame to control the line of scrimmage consistently and has the athleticism to chase down ball-carriers and make plays in the open field, abilities that he put on show in the Week 6 loss to the Washington Redskins.

The onus will now be firmly on Buckner and Thomas to continue their strong form, but they will still have plenty of assistance. Earl Mitchell brings experience as a run stuffer and D.J. Jones and Xavier Cooper have also flashed in the last few weeks. Reinforcements came with the signings Leger Douzable and Tony McDaniel and the latter in particular should aid San Francisco’s efforts against the run.

McDaniel, as a former Seattle Seahawk, should be well versed in the defense Saleh employs and has a history of playing the run well. He ranked fourth among defensive tackles in run stop percentage in 2013 and ninth in 2016, according to PFF.

Next: NFL 2017: 20 Bold predictions for Week 7

The 49ers will undoubtedly miss Armstead’s presence up front, but Buckner and Thomas are playing like elite run defenders and San Francisco has made moves to ensure they have players who can fill the void when they need to take snaps off. Armstead is a significant loss but, as long as Buckner and Thomas are in the lineup, running backs should continue to find it difficult to have success against the Niners down the stretch.