"We played like shit."

Joe Staley’s summation of the 49ers offense might simply have been referring to Sunday’s embarrassing home loss to the Rams, but it’s an equally befitting description of San Francisco’s season on Staley’s side of the ball through eight games. After producing just 10 points against what had been one of the worst defenses in football going into the week, the Niners offense ranks 23rd in offensive DVOA — their worst ranking at this point of the season in the Harbaugh era. San Francisco’s minus–46.9 percent offensive DVOA against Jeff Fisher’s Rams was their worst showing of 2014.

When you’ve struggled as much as the 49ers have on offense for most of the season, to put matters in Harbaugh lexicon, everyone has their fingerprints on it. But when attempting to explain San Francisco’s lackluster offense, you have to begin with what is supposed to be the strength of the team: the offensive line.

Pass Protection

San Francisco’s offensive line has never been great protecting the passer. The 49ers haven’t ranked higher than 22nd in Adjusted Sack Rate since any member of the current group has been in place, highlighting both the offensive line’s deficiency in this area along with the sack-prone quarterbacks San Francisco has employed over that time. Sunday’s performance against St. Louis was a microcosm of both issues.

The eight sacks recorded by Robert Quinn & Co. were the most the 49ers have allowed in a game since Harbaugh Bowl I in 2011, when Terrell Suggs and the Ravens ran roughshod over the 49ers offense to the tune of nine sacks. Those eight sacks were enough to push San Francisco’s Adjusted Sack Rate up to 9.5 percent on the season, better than only the Jaguars and the 49ers’ worst rate since Staley’s rookie season in 2007.

It’s difficult to pinpoint one specific thing the 49ers are struggling with up front, as teams are carving a path to Colin Kaepernick in a variety of ways. At times, the line is simply losing individual battles as it did on this play midway through the first quarter against the Rams:

Rookie Aaron Donald (99) tosses aside Alex Boone to pressure Kaepernick from the middle of the pocket while William Hayes (95) gets passed Anthony Davis on the edge. Kaepernick might have been able to get the ball out to his checkdown, but the pressure comes quickly with Donald and Hayes converging for the sack.

Other times it’s been what appears to be some sort of miscommunication and an inability to handle blitzes or stunts, as we see on this play early in the second quarter:

St. Louis brings a five-man blitz and looks to attack the left side of San Francisco’s line. Robert Quinn (94) and Eugene Sims (97) slant inside while Alec Ogletree (52) and James Laurinaitis (55) loop around to the outside. Marcus Martin and Mike Iupati’s feet get tangled up, Martin falls to the ground, and neither player winds up blocking anyone. Staley gets pulled inside by Quinn, leaving Frank Gore to handle the two linebackers. Needless to say that doesn’t go so well and Kaepernick gets taken down again.

There are other instances when the offensive line does enough to get the job done but Kaepernick fails to do them any favors, something that showed up on this play with the 49ers looking to put points on the board at the end of the first half:

As Kaepernick hits the back of his drop, he’s looking for Brandon Lloyd on the curl route. With a defender moving underneath the route, Kaepernick wisely pulls up on the throw. By this point, pressure is starting to get home off the edges. It’s here that the play breaks down for Kaepernick. Subtle movement up in the pocket would be enough to get out of harm’s way and find a wide-open Michael Crabtree along the sideline. A completion to Crabtree gets the 49ers up to about the 25-yard line and sets up Phil Dawson with a very makable field goal.

Instead, perhaps with visions of previous sacks still in his head, Kaepernick takes off, getting tripped up before he can get into the open field and taking a sack in a situation where the 49ers absolutely couldn’t afford one. The sack cost San Francisco valuable yardage as the ensuing Dawson attempt fell short, undoing the good work Kaepernick had done on that drive to put them in position to get points before the half.

Run Blocking

None of the issues in pass protection are especially new. They’re all problems San Francisco has dealt with over the past several seasons while still managing to put together very effective offenses. Far more concerning has been the slow disappearance of their dominant run game.

Roughly around this time in 2012, the 49ers were coming off one of the most proficient stretches running the football in league history and their offensive line was widely regarded as the best in football. Since that point, San Francisco’s rushing attack has been trending downhill. Here’s a look at some of their key rushing metrics from the last three seasons, courtesy of Football Outsiders:

Year RB Y/A Run offense DVOA Rank Adjusted Line Yards Rank Power Success Rank Stuffed Rate Rank 2012 4.74 12.6% 3 4.49 1 65% 12 17.0% 7 2013 4.06 2.3% 14 3.57 29 55% 28 23.9% 29 2014 3.82 -8.1% 20 3.82 22 42% 32 20.9% 24

Frank Gore & Co. haven’t been finding much running room and that’s been largely on the offensive line. Converting short-yardage situations (power success) and preventing tackles from being made behind the line of scrimmage (stuffed rate) are primarily the responsibility of the offensive line. How a team performs in these areas is typically a good indication of how the offensive line is doing in the run game. As you can see from the above numbers, the 49ers simply aren’t getting it done up front.

On San Francisco’s opening play from scrimmage last week, we see a zone running play to the left side. One of the key blocks on the play is the combo block of Martin and Iupati. They’re going to initially double team Michael Brockers (90) in the playside A-gap before Iupati moves up to the second level to pick up Laurinaitis.

Assigning blame along the offensive line is an incredibly difficult thing to do without knowing how the 49ers coach the play. We’re left with educated guesses at best. That said, Martin has a long ways to go to reach Brockers’s outside shoulder to seal him off. It feels like Iupati could’ve stuck with the double a bit longer to give Martin more time to gain position, but regardless it’s easy to see the play doesn’t go as planned. Brockers gets into the rushing lane, Quinn doesn’t give up much ground on the edge to Staley, and despite having sufficient numbers to get everyone blocked, the hole closes and Gore is able to gain only a single yard.

A very similar play showed up against the Rams the first time around.

Here we have another zone run, this time to the right of the offense. Aaron Donald splits the double team from Iupati and Staley. It again appears that Iupati leaves the double a little too early to make his way to the linebacker. Toss in a double whiff from Alex Boone on the other side, missing both the defensive tackle and linebacker all in one terrible looking motion, and Gore has nowhere to go.

What about power and counter, San Francisco’s bread and butter run plays? There was a point in which it just seemed unfair how much movement that the 49ers would get with their double teams on those plays. The combination of Staley and Iupati was especially potent at evacuating the defender from the point of attack. That same type of movement hasn’t been there this season.

Going back to the first game in St. Louis again, we see Donald wrecking another run play. The 49ers want to run off the double team of Staley and Joe Looney, however Donald just demolishes it and actually ends up pushing Looney backwards into the hole. Vernon Davis is unable to keep Quinn from pressing the hole from the outside and the rushing lane closes so quickly that Boone, who’s pulling from his right guard spot, isn’t even able to get through it without getting tripped up.

Outside of an above average two-game stretch against the Eagles and Chiefs, the 49ers have been terrible when they’ve tried to run the ball this season. The last three games have been especially poor. Frank Gore and Carlos Hyde have combined for 153 yards on 55 carries (2.78 yards per carry) over that stretch, with just 15 of those carries (27.3%) picking up enough yardage to be considered successful based on the down and distance. More carries (16) have gone for no gain or a loss in that time frame.

I don’t know what the answer is for the 49ers offense. But whether you think Harbaugh and Roman need to get back to relying on Gore and a run-heavy approach or that they must turn Kaepernick loose and put the ball in the hands of their young quarterback, one thing is for certain: neither approach is going to work if the offensive line continues to play as poorly as they have through eight games. And if they don’t turn things around in a hurry, the 49ers will be watching the playoffs from home for the first time in Harbaugh’s tenure.