There were a number of surprising elements to the San Francisco 49ers’ six-point loss at the hands of the NFC West-leading Arizona Cardinals. Near the top of the list was the play of the 49ers’ run defense.
This performance continued the 2015 norm of being incredibly inconsistent from week to week. In the first meeting against the Cardinals back in September, the 49ers surrendered 110 yards and two touchdowns to Chris Johnson, helping football-watching America realize that Johnson might actually be OK at football still, which was kind of weird. More recently, they allowed rookie Seahawks ballcarrier Thomas Rawls to top 200 yards, the first time in franchise history the 49ers allowed a running back to do so. Todd Gurley went for 133 and a score. Even Eddie Lacy, who has been stuck in the mud for much of the season, averaged five yards per clip on his way to a 90-yard day. And yet, there were some solid performances from Eric Mangini’s unit intermingled in there as well, most notably holding Devonta Freeman to 12 yards on as many carries.
San Francisco didn’t shut down Arizona’s stable of running backs to quite the same extent as they limited Freeman and the Falcons, but it was damn good nonetheless. Cardinals’ running backs carried the ball 26 times for 64 yards (2.46 YPC). Chris Johnson & Co. failed to find steady yardage, as only two carries reached double-digit yardage while nine runs were stopped for no gain or a loss. That was good for a success rate of 34.6 percent; in essence, the 49ers run defense turned the Cardinals’ collective of running backs into Isaiah Crowell.
A good chunk of San Francisco’s success defending the run stemmed from some excellent work in short-yardage situations. Entering the contest, the 49ers had been one of the league’s worst defenses in these situations. Opposing teams converted 72 percent of power situations — defined as third- and fourth-and–2 or less or goal-to-go situations from the two-yard line or closer — which was the sixth-worst rate in football.
The 49ers also struggled breaking into the backfield to create negative plays in the run game, doing so on only 15 percent of opposing runs, bettering only the Bears.
All of that flipped against the Cardinals. Arizona converted on just 1-of–7 rushing attempts in power situations, with the lone conversion coming on David Johnson’s third-quarter touchdown run, and even that play came after roughly 27 goal-line plays and a dozen penalties, give or take. Five of those runs were stopped in the backfield, and it started with penetration up front from San Francisco’s defensive line.
On the second play of the goal-line series that would eventually end in Johnson’s touchdown run, Arik Armstead and Mike Purcell shot into the backfield, forcing Chris Johnson to bounce outside where Tank Carradine and Jaquiski Tartt would clean up the mess for a loss of three.
After a Tramaine Brock penalty, the Cardinals made the curious decision of sending out an additional quarterback in an area of the field where you’d typically like to have all of the extra blockers you can get. Thankfully, the 49ers front wasn’t confused. Michael Wilhoite gets a good read on the run, allowing him to shoot the gap before Mike Iupati has an opportunity to get outside. Kenneth Acker, who paid as much attention to Carson Palmer the wide receiver as he’d likely pay to you or me out there, cuts off any hope Johnson had of outrunning Wilhoite to the pylon, and he goes down for another loss.
Gerald Hodges, acquired via trade with the Vikings back in October, only played eight snaps in this game, but he made the most of them with a pair of excellent plays at the goal line. On the first one, pictured above, Hodges times the snap perfectly, bursts into the backfield and upends offensive-lineman-playing-fullback A.Q. Shipley. The havoc created by Hodges in the backfield prevents David Johnson from getting through a clean lane into the end zone, and gives NaVorro Bowman and Aaron Lynch time to shed blocks and make the tackle short of the goal line.
Later in the game, Hodges again showed excellent play recognition.
Here, the Cardinals are trying their luck to the outside with a toss play. The moment Hodges sees right tackle Bobby Massie and tight end Jermaine Gresham take a drop step to pull outside, he turns and sprints to beat them to the spot. Without that immediate recognition, the 49ers defense gets sealed inside and Johnson waltzes into the end zone. Instead, Hodges makes the play for a two-yard loss.
Whenever you’re allowing less than 2.5 yards per carry, you’re doing more than just stepping up your game in short-yardage situations, of course. San Francisco ceded a still-very-solid 3.7 yards per run on 18 carries in non-power situations, and just about everyone in the front seven pitched in with effective performances.
NaVorro Bowman led the way with five run stops on the day, and the play above was perhaps his most impressive. Bowman is moving toward the play side before any other 49ers defender, which keeps guard Ted Larsen from reaching him on the second level. Bowman expertly navigates through the traffic, squares up Chris Johnson, and makes the tackle for no gain.
Bowman’s running mate on the inside, Michael Wilhoite, also put together one of his better days against the run. Wilhoite contributed three run stops and led the team with two run defeats, shooting through the A-gap to record one of those defeats on this play in the second quarter:
On the defensive line, the player who impressed me most was Ian Williams. Not only did Williams do yeoman’s work in absorbing double teams for much of the day to allow the linebackers behind him to make plays, but he got in on the action several times as well. Williams’s three run stops matched Wilhoite for second on the team, as he showed a knack for locating the ballcarrier and shedding his block to make the tackle.
On this play midway through the fourth quarter, you see Williams aligned in the B-gap on the inside shoulder of right tackle Bobbie Massie. When David Johnson sees Williams’s helmet to the inside, he looks to cut through a lane on the outside. Without the play of Williams to fight across the face of Massie and make the tackle, Johnson ends up one-on-one with Tartt in the open field and is one missed tackle away from a big gain. Instead, the play goes for a measly one yard.
Several other members of San Francisco’s front seven contributed to their success in stopping Arizona’s rushing attack. It was a bit of a surprise that Mike Purcell, who we saw shoot into the backfield in the first GIF of the article, filled in for the injured Glenn Dorsey in lieu of Arik Armstead, but he played well. Aaron Lynch, who had another nine pressures as a pass rusher on the day, didn’t show up in the box score a whole lot, but continued to do good work setting the edge in the run game. As is frequently the case with good run defense, the entire front seven got involved.
As I mentioned at the top of the article, the problem with San Francisco’s run defense this season, like so many other aspects of this team, is that they’ve been maddeningly inconsistent. I wrote earlier about the 49ers’ extreme home/road splits, and their run defense certainly isn’t immune to those swings in performance. San Francisco has been above average against the run in all but one of their six home games this season, according to Football Outsiders’s opponent-adjusted metrics, but has been below average in every one of their five road games.
If those splits hold, it won’t bode well for a repeat performance against the run this week in Chicago versus the surging Bears and their 10th-ranked run offense. They say good defense travels, which seems like a good time to remind you that even after one of their best defensive efforts of 2015, only the Saints have been worse on defense this season. Whether it’s on the ground or through the air, it’s likely going to take a good amount of luck for San Francisco to slow down Jay Cutler & Co. in Week 13.