Breaking Down San Francisco 49ers' Best Replacement Options for Justin Smith

San Francisco 49ers' longtime defensive end Justin Smith is gone. The 35-year-old veteran announced his retirement from the NFL via a team statement last Monday.

Smith's decision isn't exactly a shock. The five-time Pro Bowler had hinted at retirement as far back as the final regular-season game on San Francisco's 2014 schedule—news that was first reported by NFL Network's Alex Flanagan last December:

The 49ers have had ample time to prepare for this departure and have been readying their roster well before Smith made his final decision. 

But which former supporting cast member will be the best fit in Smith's wake? Is it possible to expect a rotation of sorts along the 49ers' defensive line?

Some D-line members are best suited to remain backups in 2015 and beyond. A few, however, could make Smith's retirement not hurt as bad as one may think.

Jeff Chiu/Associated Press

Preparing for Life After Smith

Smith's age was enough to convince the 49ers' front office that a long-term replacement would be needed sooner rather than later.

In 2013, San Francisco attempted to fill this need via the NFL draft. General manager Trent Baalke picked up D-linemen Tank Carradine and Quinton Dial in Rounds 2 and 5, respectively. The 49ers also added veteran nose tackle Glenn Dorsey and British Olympian Lawrence Okoye prior to the season.

The following year, San Francisco took a Round 7 flier on defensive end Kaleb Ramsey.

Free agency provided the 49ers with D-lineman Darnell Dockett. Then Baalke capped off the depth with a 2015 first-round selection of former University of Oregon DE Arik Armstead—a massive physical specimen at 6'7" and 298 pounds.

The deep cast of recent additions along with incumbent veterans gives new head coach Jim Tomsula a good amount of flexibility in determining who starts for Smith. 

Prior to Smith's departure—and certainly in recognition of its possibility—Tomsula noted via Matt Barrows of the Sacramento Bee that the 49ers' D-line was as deep as he could remember.

But this is something for which the 49ers have been preparing as far back as 2013.

According to Jeff Deeney of Pro Football Focus, San Francisco had been cutting Smith's snap-count percentage following the 2012 season. That year, Smith played 87.8 percent of snaps per game. The number decreased to 73.3 percent the following year and all the way down to 66.7 in 2014:

The fewer snaps in recent years likely explain why Smith's tackling totals decreased between 2012 and 2014. But Smith was able to register more sacks in his final two seasons despite playing on fewer downs, as indicated by the chart below.

Year	Games	Tackles	Assists	Sacks
2008	16	50	23	7.0
2009	16	40	15	6.0
2010	16	57	13	8.5
2011	16	45	13	7.5
2012	14	47	19	3.0
2013	16	32	17	6.5
2014	16	28	15	5.0
Total	110	299	115	43.5

Perhaps Smith was more rested. Perhaps he was able to pick up the slack left off by the on- and off-the-field absences of fellow 49ers pass-rushers. One may never know.

Marcio Jose Sanchez/Associated Press

The Options to Replace Smith

"Replacing" Smith will be all but impossible. There are those familiar with Smith and the 49ers' organization—former 49ers head coach Jim Harbaugh is one person—who feel he is destined for the Hall of Fame.

But the deep cast of players on San Francisco's roster gives Tomsula plenty of competition as the team enters training camp and the preseason.

And one cannot forget that the 49ers will be seeking a long-term replacement for former 49ers DE Ray McDonald.

San Francisco has 10 D-linemen on its current roster, per the team's website. From this cast, players like Armstead, Okoye, Ramsey and Marcus Rush have yet to take a regular-season snap. And the final three figure to be little more than depth options in coming seasons.

Player	Games	Tackles	Assists	Sacks
Arik Armstead (collegiate)	13	25	21	2.5
Tank Carradine	9	16	1	3.0
Quinton Dial	14	21	9	2.0
Darnell Dockett (w/ Arizona -- DNP)	0	0	0	0
Glenn Dorsey (DNP)	0	0	0	0
Tony Jerod-Eddie	16	12	8	0
Lawrence Okoye (Practice Squad -- DNP)	0	0	0	0
Kaleb Ramsey (DNP)	0	0	0	0
Marcus Rush (collegiate)	13	22	15	7.5
Ian Williams	9	18	4	1.0

But Armstead has to warrant additional consideration for No. 1 on the depth chart given the team's investment in him.

True, the rookie's size and prowess suggest he could emerge as something special at the pro level. Perhaps he becomes the worthy heir to Smith's role in San Francisco's 3-4 defense—locking up multiple blockers and allowing fellow pass-rushers to pressure the quarterback.

Yet this might take time. Armstead's numbers in college do not suggest that he played at the highest of levels. Over three seasons at Oregon, Armstead totaled just four sacks and 10.5 tackles for a loss. Grant M P rewteeted this Justin Smith quote, via Cam Inman:

The 49ers simply won't just hand the starting job to Armstead, per Tyler Emerick of 49ers.com. He'll have to earn it. But the 49ers would prefer this sooner rather than later.

San Francisco could also go with a veteran to start in Smith's place. Dockett is one such possibility. The 33-year-old veteran has notched 40.5 sacks over his storied career. But will his age and a missed 2014 campaign due to injury limit Dockett to being just a situational pass-rusher?

Rick Scuteri/Associated Press

Dorsey could also move back to end—a position he played with regularity prior to signing with the 49ers. But Dorsey's strengths are primarily against the run and not so much as a pass-rusher. He has just six sacks over his seven-year career. And, like Dockett, injuries held Dorsey out for the entirety of 2014.

Dial is a likable option to take over a starting end position. Tomsula sees Dial "more as an end," per Emerick, which suggests that Dial could shift over from the nose tackle position to occupy the void. 

But would this be the best option for San Francisco's defense on Smith's side of the line?

Jason O. Watson/Getty Images

The Best Option: Tank Carradine

2015 will hopefully be the year in which Carradine emerges as a household name.

Like Armstead this year, the 49ers invested heavily in Carradine when they drafted him in Round 2 of the 2013 draft. Carradine was redshirted his rookie season, which probably hindered his development in 2014. Carradine saw action in just nine games last year.

But those nine games showed some promise and revealed plenty of Carradine's potential late in the season. He finished the year with three sacks and 11 tackles over the final four games of San Francisco's schedule.

Taylor Price of 49ers.com describes how Carradine might fit into the 49ers' situation this year:

"

Tank Carradine is definitely in the mix to be a starter, as is Darnell Dockett. The former Florida State standouts, who are eight years apart in age, appear to be hungry to start for different reasons. Carradine is looking to prove himself as an every-down player in his third season. Dockett, the 12-year veteran, wants to prove that he can still play at a high level after missing the entire 2014 season with a torn ACL.

"

And the fact that Carradine, along with linebacker Aldon Smith, recently received pass-rushing advice from Hall of Famer Charles Haley (h/t Cam Inman of the San Jose Mercury News) doesn't hurt either.

Dockett might bring the veteran prowess. And perhaps he'll be best suited to occupy McDonald's spot on the opposite side of the line. But the damage should be left to Carradine in Justin Smith's void. 

Marcio Jose Sanchez/Associated Press

If things work out, Carradine will be performing a similar role that Smith filled. This task will hopefully open up the lanes that Aldon Smith enjoyed so frequently in years prior.

Putting things bluntly: It's Carradine's time to shine.

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In all likelihood, the 49ers will employ a rotation of sorts. This will allow the defense to utilize its deep cast of talent and keep each specific player rested and fresh. 

Unlike previous seasons, San Francisco won't have to rely on a high snap count for any one D-line player as was the case with Justin Smith in 2011 and 2012. Rotating players into the mix should keep veterans like Dockett and Dorsey fresh while allowing them to maximize their respective talents.

Such a rotation will also give younger players like Armstead a chance to work into the defense without being too much of a liability out of the gate.

Yet the 49ers have the chance to let Carradine loose in 2015. The physical abilities are there. All that is left is to hope the numbers match Carradine's talent.

If Carradine can seize this, Smith's retirement will be that much easier to swallow.

All statistics, records and accolades courtesy of Pro-Football-Reference and Sports-Reference.com unless otherwise indicated. 

Peter Panacy is a Featured Columnist for Bleacher Report, covering the San Francisco 49ers.

Follow him @PeterPanacy on Twitter.