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Evaluating the 49ers defense through the first quarter of the 2015 season

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With the first quarter of the 2015 season in the books, it's time to take a step back and see where the 49ers stand in the big picture. Today we look at the defense.

Somehow, we’re already a month into the 2015 NFL season, and we’re using that as an excuse to step back and look at where the San Francisco 49ers sit in the NFL’s bigger picture after four games. Yesterday, we looked at Colin Kaepernick and a struggling offense. Today, we’re focusing on Eric Mangini’s defense.

San Francisco’s defense has been all over the map so far. Blitzing and confusion reigned supreme against the Vikings, as Teddy Bridgewater was unable to exploit vulnerabilities down the field. That changed in dramatic fashion against the Steelers and Cardinals, with Ben Roethlisberger and Carson Palmer looking like they were playing Madden on rookie difficulty. And finally, things settled somewhere in the middle during a commendable performance against Aaron Rodgers and the Packers.

While our last impression of this defense was a positive one, that first-month roller coaster still leaves the 49ers as one of the worst defenses in football so far. San Francisco has allowed 96 points through four games (officially 110, but 14 of those points came off Kaepernick pick-sixes). Split that into a per-drive figure, and their 2.33 points per drive is the sixth-worst mark in football. According to DVOA, Football Outsiders’ opponent-adjusted efficiency metric, the 49ers have the league’s fourth-worst defense so far, landing in the bottom five against both the run and pass.

The sheer volume of turnover on this side of the ball makes it pointless to compare where San Francisco’s performance in 2015 differs from previous seasons. Struggles were inevitable when dealing with that much change all at once. The real question becomes: Is there any reason to think the 49ers defense will be better over their final 12 games?

The answer depends on your expectations for better. The 2015 49ers defense won’t approach the dominant level of play they exhibited under the previous coaching regime, and even becoming an above-average unit is probably a stretch. But can they approach mediocrity and not be one of the worst defenses in football? I think so, and that starts with Eric Mangini.

Unlike what we’ve seen from San Francisco’s offense, Mangini has shown a willingness to change his approach from week to week. Throughout the offseason, the theme for Mangini’s defense was confusion. "Coach Mangini’s thing is that we’re going to cause confusion," safety Antoine Bethea said during a media session this offseason. "The opposing offense won’t know what we’re going to do each down. That could be bringing pressure or dropping eight in coverage but it’s all about keeping the offense on their heels. That means a lot of movement and everyone having to know what everyone else is doing."

That’s exactly what we saw in Week 1. San Francisco crowded the line of scrimmage with defenders, mixing big blitzes with plays where everyone bailed back into coverage. Mangini looked to carry that success to Pittsburgh by adopting a similar approach, keeping the pre-snap disguise but ditching the blitz. Roethlisberger wasn’t confused, however, and the 49ers were torched repeatedly for big plays. Eric Reid and Antoine Bethea’s pre-snap alignment in the box left them out of position on deep throws down the sideline, and Antonio Brown & Co. took advantage.

More significant tweaks came in Arizona the following week. Reid and Bethea backed up to more typical safety depth on most snaps to help put a lid on the big plays, sub-packages spent less time on the field, and the blitz rate kicked back up to 50 percent. Unfortunately, those adjustments failed, too. Palmer exploited huge holes in the middle of San Francisco’s zone coverages to put up big passing numbers of his own.

Finally, things came together last week against the Packers. The pre-snap movement disappeared almost completely, as did the Tampa-2 coverages and three-man pass rushes that were so ineffective in the first three games. Instead, Mangini’s unit took a Fangio-esque approach, sitting in nickel for most of the game and giving Rodgers the same pre-snap look on nearly every snap before rotating to a variety of coverages after the snap. Execution was markedly improved. The 49ers did a better job of recognizing route combinations and locating receivers when dropping into their zones. The results — holding a Rodgers-led offense to 17 points and 224 passing yards — were a drastic departure from what we saw in the previous two games.

Amidst a coaching staff that has appeared to be in over its head so far in many different facets, Mangini’s efforts should be commended. Not all of his adjustments have been good ones, far from it actually, but he hasn’t resigned himself to doing the same things every week and expecting different results.

A willingness to adapt and make adjustments is a great start, of course, but those changes must translate to notable improvement in several areas of their performance if the 49ers hope to get out of the cellar in nearly every relevant defensive metric. Let’s run through some of the most notable areas they could use a boost.

Turnovers

San Francisco has generated a takeaway on just 5.0 percent of opponent drives, the second-lowest rate in football. Tramaine Brock and Kenneth Acker each have an interception, but both came in relatively meaningless situations. Brock picked off Bridgewater late in Week 1 when the game was already decided. Acker’s interception came with one minute left in the first half against the Cardinals, with the 49ers already down 21 points.

Those are the only two takeaways the 49ers have on the season. They’ve forced two fumbles, but have yet to recover one. There’s no reason to think San Francisco is "due" to start creating turnovers. It’s also difficult to ask this defense to simultaneously prevent the big plays that were their downfall in Weeks 2 and 3, and be more aggressive to try and generate more turnovers. But an increase in takeaways would help this unit tremendously.

Red zone

When you look at San Francisco’s performance by field zone, they’ve actually been slightly below average over the first 80 yards of the field, according to Football Outsiders’ DVOA. However, things fall apart once the opposing team reaches the red zone. The 49ers are allowing 5.73 points per red-zone trip, the fifth-worst figure in football, and opposing offenses are putting the ball in the end zone on 73.3 percent of their red-zone appearances.

Teams don’t get many plays in the red zone to prove their worth, yet their performance in this area has a disproportionate impact on the final result. If the 49ers can start forcing some more field goals and their red-zone performance can catch up with their performance in other areas of the field, that would be a big step toward respectability.

Big plays

The easiest way to put points on the board is by getting big chunks of yardage all at once. Big plays destroyed the 49ers defense against the Steelers and Cardinals, and they gave up 76 points. On the season, San Francisco has allowed 17 passes of 20 yards or more, which works out to just about one every eight attempts (12.9 percent). Only the Lions have given up big plays through the air more frequently.

It remains to be seen whether Mangini’s approach against the Packers becomes the norm over the rest of the season, but keeping Reid and Bethea back deep where they appear more comfortable should help alleviate this issue to some extent.

Play worse offenses

It should come as no surprise that after lining up against Roethlisberger, Palmer, and Rodgers, the 49ers have faced the league’s toughest slate of opposing offenses, per Football Outsiders. All three of those teams currently rank among the NFL’s six best offenses. That’s a rough start for a defense that’s trying to piece together a bunch of new parts in a completely new scheme.

As I’ve mentioned before, the list of opposing quarterbacks on San Francisco’s schedule is a daunting one. Eli Manning and Joe Flacco are up next. Russell Wilson (twice), Matt Ryan, and another bout with Palmer all come before December hits. There aren’t any truly bad offenses on the schedule until San Francisco travels to Chicago and Cleveland late in the year. That said, most of these offenses are more flawed than the ones the 49ers have faced thus far. Atlanta is a top-five offense, but most of the others have been somewhere in the middle of the pack so far. It’s not the sort of schedule that will make this defense look great, but there should be a slight reprieve from an incredibly difficult first month.