The battle for the trenches that could decide 49ers–Chiefs rematch

Their devastating loss has been parsed every which way, but it’s fair to say that the 49ers didn’t handle Kansas City’s full-scale defensive barrage well enough in Super Bowl LVIII.

The Chiefs blitzed over 52% of the time and registered nine unblocked pressures against 49ers quarterback Brock Purdy. Coordinator Steve Spagnuolo’s defense successfully disrupted the 49ers’ two third-down plays: one late in regulation that could’ve set up a game-winning field goal attempt and one in overtime that shifted the balance of power from Purdy to Kansas City QB Patrick Mahomes.

Purdy is outplaying Mahomes this season, yes. But he was already statistically better than his Chiefs counterpart last season, when Kansas City won the championship. That served as a simple reminder that this a team sport, and pass protection and run blocking — where the Chiefs collectively outperformed the 49ers — are key components of any title bid.

Kansas City is succeeding up front again this season. Their offensive line ranks No. 1 and No. 2 in ESPN’s pass-block and run-block win rates, respectively. Their defensive line again features perennial All-Pro Chris Jones, who’s now wrecked the 49ers in two Super Bowls.

The Chiefs’ O-line doesn’t score quite as well in other metrics, such as Pro Football Focus grade, but it has still managed a composite No. 8 ranking.

And that’s where the intrigue of an evolving matchup builds. The 49ers, whose O-line ranked in the twenties over both seasons that ended with losses to Kansas City, now rank No. 10 — not far from the Chiefs.

If there’s a single player representative of the 49ers’ upward shift, it’s rookie right guard Dominick Puni. He’s one of 12 qualifying NFL guards to have not allowed a single sack through the first six weeks of the season.

For the first time since 49ers coach Kyle Shanahan took over in 2017, in fact, the team is enjoying above-average right guard play. Puni also ranks No. 8 of 61 qualifiers by PFF’s run-blocking grade.

That’s paired well with 49ers right tackle Colton McKivitz, who struggled last season but has surged to No. 17 of 52 qualifiers in run blocking. The 49ers are running more effectively than ever to the right side, averaging about 6 yards per carry.

“Puni is a huge part of that, the way he presses some landmarks,” McKivitz said this week. “It’s been fun playing with him. Teams know that we were pretty dominant-heavy with the left side. So to be able to switch it up and go right, with Kyle having the same confidence in the right side as the left, is huge.”

It’s especially important against a defense like Kansas City’s, which is intent on playing as much man-to-man coverage as possible against the 49ers, who can only force the Chiefs to move into more zone alignments — which are ideal for Purdy and the pass offense — if they run the ball effectively.

Kansas City’s run defense ranks No. 8 in expected points added (EPA) per play, a significant uptick from last year’s No. 28 ranking. Defensive tackle Mike Pennel, whom the 49ers consider one of the best run-stopping interior specialists in the league, fortify against stalwarts like Jones.

“[Jones] is a hard dude to block, man,” McKivitz said. “He’s one of the strongest players I’ve ever played.”

Jones lines up across the entire front. He’ll likely test Puni and McKivitz, too. (It was an error at right guard by the 49ers’ Spencer Burford that allowed Jones a free rush at Purdy during their final offensive play of last season.) The 49ers used defensive tackle Evan Anderson to emulate Jones on the scout team this week, and it was the rookie’s first time lining up at defensive end.

“He just shows up in the big moments,” Puni said of Jones. “That’s his X factor and that’s what he brings to the table.”

Jones isn’t Kansas City’s only versatile defensive weapon. Spagnuolo’s entire unit is adaptable at key junctures. Entire tendencies will shift on key late-game downs. Pressures will come from unpredictable angles — and they’re sure to come frequently, just like they did in the Super Bowl.

Spagnuolo “brings a lot of [Cover 0] in the red zone and a lot of [Cover 0] coming out,” said 49ers center Jake Brendel, who’ll be in charge of setting the team’s protections against Kansas City. “We just have to be ready for those looks and make sure we have the outlets that we need for the quarterback. And in the run game, we need to be sure to get a body on a body.”

On the other side, the 49ers’ defensive line will face its biggest test of the young season. Kansas City’s offensive line is the rare NFL unit without a glaringly poor performer, as evidenced by the percentile scores in PFF’s pass-blocking efficiency across the front:

Left tackle Wanya Morris owns the worst score of the group, but even that ranks near average. He’s allowed just one sack and eight pressures. The Chiefs are particularly strong in the middle, where center Creed Humphrey and tackle Joe Thuney — who didn’t play against the 49ers in the Super Bowl — are among the NFL leaders at their respective positions.

Is the 49ers’ defensive front, which generated big pressure against a significantly worse Seattle O-line last week, better prepared to stymie the Chiefs than it was back in February?

Star edge rusher Nick Bosa provided one hint.

“We definitely have a plan for the zone read this time,” he said, referring to fourth-down play that Mahomes converted in overtime to keep the Chiefs alive.

A few snaps after that, Kansas City scored the winning touchdown out of a similar alignment. They stormed off the field with the Lombardi Trophy. The 49ers left crushed.

Crunch time had gone to the Chiefs.

“They’ve come through and we haven’t,” McKivitz said. “It sucks, but you learn from things, man. That’s why they’re called scars.”

On Sunday, the 49ers will aim to apply those tough lessons. If they succeed, it’ll likely be because they closed the gap with Kansas City up front.