Grant Cohn: Next step for 49ers is to complete the defense

SANTA CLARA — And the winner of the prestigious 49ers Coach of the Year Award, which I just made up, goes to defensive coordinator Robert Saleh.

This was no easy decision. Head coach Kyle Shanahan was a serious candidate. But Shanahan has Jimmy Garoppolo, and Saleh has only half a defense.

Before I explain about the defense, let me explain about Garoppolo.

He, not Shanahan, is the main reason the offense has performed well lately. Before Garoppolo became the starting quarterback, the 49ers ranked 28th out of 32 teams in points scored. Not good.

The past three games with Garoppolo at QB, the 49ers rank fifth in points scored. He's the difference on offense.

Saleh is the difference on defense.

Since the bye week, the 49ers defense has given up a respectable 22 points per game even though it's nowhere near complete.

It's just a run defense. The best players line up at defensive tackle (DeForest Buckner, Earl Mitchell, Solomon Thomas) and linebacker (Reuben Foster). That's the middle of the defense. The core.

The Niners run defense has been among the best in the NFL since the bye. It has allowed only 3.3 yards per carry, and it hasn't allowed a team to rush for more than 92 yards in five consecutive games. The Niners haven't been this good against the run since 2011 when Vic Fangio was coaching the defense and Justin Smith and Patrick Willis were in their prime.

That 2011 defense was complete. It could stop the run and pass. In addition to Smith and Willis, it had a dominant edge rusher — Aldon Smith — and a Pro Bowl cornerback — Carlos Rogers.

Saleh's defense doesn't have its version of Aldon Smith and Carlos Rogers. Doesn't have talented defensive ends and cornerbacks. Isn't equipped to defend an NFL passing attack.

It's a partial defense.

Saleh knows this.

'When people talk about building a really good defense,' Saleh said Thursday, 'you get those guys in the middle of your defense (first). That's good enough to get you to third down. Corners and edge rushers are what get you off the field. They're the ones that get you off in two-minute (situations). They're the ones that win in the red zone.

'We get to third down very, very easily. We need to learn how to close the door on third-and-12 where there is zero chance an offense can get a first down. Two-minute situations where even if we're rushing four and (the offense is) trying to bleed the clock, we're still capable of getting off the field because the edge rush and the corners are just straight lock down.'

The lack of lock-down corners and edge rushers defines the limit of Saleh's defense. As well as it has played against the run, it continues to struggle against the pass and on third down and in the red zone.

Since the bye, the 49ers defense has allowed an average opponent quarterback rating of 91.6 (not good), a third-down conversion percentage of 39.3 (also not good) and a red-zone touchdown percentage of 84.6 (really not good).

If only the Niners had more than half a defense.

With the right additions at cornerback and edge rusher, the 49ers could go to the Super Bowl next season.

Remember, Bill Walsh won his first Super Bowl with defense. That 1981 team ranked second in total defense and just 13th in total offense.

The previous season, 1980, the 49ers ranked 27th in total defense.

How did they make such a drastic defensive improvement in only one year?

They added corners and edge rushers, that's how.

With their first two draft picks, the 49ers took Ronnie Lott and Eric Wright, who combined to start 32 games at cornerback and intercept 10 passes as rookies in 1981.

Midseason, the 49ers traded for 29-year-old defensive end Fred Dean. He recorded 12 sacks in 11 games for the Niners. He completed the defense.

The 49ers can follow Walsh's blueprint this offseason by adding a corner in the draft and a veteran edge rusher in the trade market or free agency.

If the 49ers beat the LA Rams on Sunday (the Niners probably will win; the Rams won't play their best players), then the Niners will have the 10th or 11th pick in April's draft. At that spot, the Niners can take Iowa cornerback Joshua Jackson — a tall corner t 6-foot-1 who intercepted seven passes this season as a junior in college.

In free agency, the 49ers can sign Demarcus Lawrence, a 25-year-old edge rusher who recorded 14.5 sacks in 15 games this season with the Dallas Cowboys. The Cowboys currently don't have enough cap room to re-sign Lawrence this offseason.

Lawrence and Jackson would make the 49ers defense whole.

Imagine what Saleh could do with a whole defense.

Grant Cohn covers the 49ers for The Santa Rosa Press Democrat and Pressdemocrat.com. You can reach him at grantcohn@gmail.com.