Who Will Win San Francisco 49ers' Right Defensive End Battle?

Justin Smith announced his retirement Monday afternoon, per 49ers.com. Which player will replace him at right defensive end in the San Francisco 49ers’ 3-4 defense?

Here’s a breakdown of each contender’s chances.

Contender No. 1: Arik Armstead

The 49ers drafted former Oregon defensive end Arik Armstead with the 17th pick this year. Teams typically expect top-20 picks to start right away, especially if a starting job is available.

The Niners have two starting jobs available on the defensive line—right defensive end (Justin Smith retired) and left defensive end (Ray McDonald is a Chicago Bear).

But Armstead probably won’t start at either position in 2015. 49ers general manager Trent Baalke greased the wheels for that outcome hours after he drafted Armstead.

“To really get the techniques down to play that position the way our guys have to play it, there is a learning curve,” Baalke said. “Oregon, they do a lot of similar things that we do. The learning curve for him should be a little bit quicker. But at the same time, there is a lot of development that has to take place.”

Why a lot of development?

“You’ve got a young man who hasn’t spent a lot of time in the weight room,” said Baalke. “He’s been on the courts. You’ve got a young man that hasn’t started a lot of games. He chose to come out early. There is going to be some development to this process, but we are well-aware of that and feel very confident that he’s going to come in and learn how to strain and play at this level.”

Baalke made sure to remind everyone Armstead has been a full-time football player just for one year and that next season would be his senior season in college. The Niners will get away with Armstead’s development phase for a season or two.

Contender No. 2: Darnell Dockett

Former Arizona Cardinals defensive linemen Darnell Dockett might seem like the favorite to replace Justin Smith.

After all, Dockett played Justin Smith’s position for the Cardinals. And next season Dockett is scheduled to earn by far the biggest base salary—$3.25 million—of any defensive lineman on the Niners.

But Dockett turns 34 on May 27 and still is rehabbing an ACL he tore in August.

Even when he’s healthy, he isn’t particularly good at stopping the run. He’s a one-gap penetrator, not a two-gap run-stuffer. The Niners want all three down linemen in their base defense to be run-stuffers.

Dockett is an interior pass-rusher. He probably is a better fit to play in the Niners’ nickel and dime defenses in passing situations.

Contender No. 3: Tank Carradine

When the 49ers drafted Tank Carradine in the second round of the 2013 draft, the perception was the Niners drafted him to replace Justin Smith after he retired.

Like Smith, Carradine was a 4-3 defensive end in college who bulked up to play defensive end in the 49ers’ 3-4 defense.

But Carradine had a torn ACL when the Niners drafted him. He didn’t receive his first playing time until Week 10 of his second season. And he has played only 146 snaps during his career, per Pro Football Focus.

Carradine will be a free agent after the 2016 season, so the Niners need him to contribute in 2015. And he will, according to Matt Barrows of the Sacramento Bee. “On the right side, the plan right now is for...Carradine to enter in nickel situations,” Barrows wrote.

In other words, Carradine probably will play in the sub-packages, not the base defense.

If Carradine excels as a pass-rusher in the sub-packages and also shows he can stop the run, the Niners might make him Justin Smith’s full-time replacement. But if Carradine flops in the sub-packages, the Niners probably will replace him with Dockett.

Contender No. 4: Glenn Dorsey

Matt Ludtke/Associated Press

According to Barrows, Glenn Dorsey is the front-runner to replace Justin Smith next season “on base downs.”

Dorsey missed last season with a torn biceps. The season before, he earned a plus-10.6 run-defense grade in only 530 snaps, per Pro Football Focus. He played nose tackle.

Before Dorsey came to the Niners, he was the right defensive end in the Kansas City Chiefs’ 3-4 defense. And he was a good run defender at that position. He’s a good run defender at any position on the defensive line.

But he’s not a legitimate replacement for Justin Smith. Smith was a terrific pass-rusher in the 49ers’ sub-packages. Dorsey is not a pass-rusher, so although he probably will replace Smith in the base defense, Carradine most likely will replace Dorsey in the sub-packages.

One player alone cannot replace Justin Smith.

All quotations obtained firsthand unless otherwise noted.

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