When Arik Armstead went down with an injury in Week 4 against the Los Angeles Rams just one week after Javon Kinlaw sustained an injury in Week 3, San Francisco had immediate depth concerns alongside the interior of their defensive line, which had been the heart of their run defense over the past few seasons.
To begin the 2021 season, the 49ers played Arik Armstead primarily at "big end" and allowed over 100 yards rushing in seven of their first eight games, beginning the year 3-5 and at risk of missing the playoffs.
When Armstead was moved to a primarily interior defender, the 49ers allowed 100 yards rushing to an opponent just once, and that was only due to a 73-yard rushing touchdown from Travis Homer on a fake punt in Week 13.
Fast-forward to the 2022 season and the 49ers faced a similar predicament as Armstead has missed eight consecutive weeks, while Kinlaw was placed on Injured Reserve and hasn't returned since.
The Wake-Up Call
After a strong showing from the defense in a 37-15 Week 5 victory over the Carolina Panthers, the 49ers were dealt a tough hand in their following opponent—the Atlanta Falcons. Atlanta was the best opposing offensive line and rushing attack they had faced up to that point, and they entered the game without Nick Bosa, Armstead and Kinlaw.
The results were predictably bad, as the Falcons ran for 168 yards on 40 attempts, dominating the line of scrimmage en route to a 28-14 victory over the 49ers.
Bosa returned the following week, but a heavily injured 49ers squad struggled once again against a Chiefs offense known for their ability to stretch the field, allowing 112 yards on the ground on only 21 attempts in a blowout 44-23 loss.
In both losses, tackling was a primary issue, as well as setting the edge, which allowed opposing offenses to impose their will and dominate the trenches.
The return to "elite" status
At 3-4, and the division in peril due to a surging Seattle Seahawks team, the 49ers needed a change, and it stated with the defense—specifically run defense.
During that time, it was clear that both Arik Armstead and Javon Kinlaw were in no shape to return imminently, meaning the current defensive linemen needed to step up and make plays in order to return the run defense to its early-season dominance.
Kevin Givens, who was a standout during training camp, was the figurehead of San Francisco's transition, as he and Hassan Ridgeway began earning starts on the interior following the injuries.
In a way, Week 8 was similar to San Francisco's dominant performance last year in Week 10, when the 49ers were 3-5 and on the verge of a failed season.
The 49ers got their run defense clicking, allowing just 56 yards on 2.7 yards per carry, which effectively limited the Rams' offense, especially in the second half where they were blanked in a 31-14 rout.
The dominance only began there, as the 49ers allowed 51, 67, and 63 yards on the ground in subsequent weeks, despite facing the likes of Austin Ekeler in Week 10 and Alvin Kamara in Week 12, allowing just 2.9 yards per carry in those matchups.
During that four game stretch, the 49ers have miraculously failed to allow a single second-half point, which included a 4 quarter shutout over the New Orleans Saints last weekend.
Is the 49ers defense better than their early season marks?
The resurgence of the 49ers' rushing defense has cemented them as the top team in yards allowed against the run, giving up just 79.5 yards per game on the ground over the season.
However, over the past three games, the 49ers have done even better than their regular season mark, allowing just 60.3 yards per game on the ground.
On the season, the 49ers have allowed just 3.3 yards per carry, which is, by far, the best mark in the NFL. But, over the past three games, that number has decreased to just 2.9 yards per carry, signifying how dominant the defensive line has been against the run, despite missing Arik Armstead and Javon Kinlaw.
The numbers aren't just impressive for the run defense, however, as the 49ers lead the league in yards allowed per game (281.7) by a wide margin, and just 270 yards per game over their past three outings
The defense has been efficient as well, having allowed just 4.7 yards per play (#1), and just 4.5 yards per play over the last three games.
Kevin Givens, Hassan Ridgeway, and the other interior defensive linemen that the 49ers have utilized to sustain success have been a significant reason why the 49ers have been able to go on a four-game winning streak.
While the winning streak could come to a halt this weekend, the run defense should only improve when the Armstead returns this weekend.