SANTA CLARA -- The 49ers drafted two prototypical 3-4 defensive linemen, Arik Armstead and DeForest Buckner, in the first round the past two years, which suggests they are married to a 3-4 scheme for the near future.
The problem is that they don't have a nose tackle -- the player lining up there now, Glenn Dorsey, isn't signed beyond this season -- or any truly great prospects at outside linebacker, the two spots that make a 3-4 defense distinct.
That, in turn, has led to questions about whether the team might switch to a 4-3 defense next season. Any conversion would depend on the coaching staff -- does Jim O'Neil, who is a 3-4 advocate, keep his job? -- and perhaps whom the 49ers add in free agency and the draft.
But moving to a 4-3 certainly is possible. Based on who is under contract for 2017, this is what a starting lineup could look like:
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Defensive line: LDE Arik Armstead, DT DeForest Buckner, DT Quinton Dial, RDE Aaron Lynch.
Notes: Armstead is bigger than a traditional 4-3 defensive end, but he's got enough movement skills to play on the edge of the defense. He and Buckner could pair up at defensive tackle in nickel and dime defense just as they did earlier this year. The alignment would make Tank Carradine a 4-3 defensive end, which is the position he played at Florida State and the one at which he'd be most comfortable. Eli Harold also would go from 3-4 outside linebacker to 4-3 defensive end as would Ronald Blair.
Linebackers: SAM Ahmad Brooks, MIKE NaVorro Bowman, WILL Ray-Ray Armstrong*
Notes: Brooks played inside linebacker in college (watch this and this), entered the NFL with the Bengals as an inside linebacker and dabbled at the position with the 49ers, notably in goal-line situations against the Panthers in the 2013 playoffs. In this scenario, he'd be the team's strong-side or SAM linebacker (and probably would have to lose weight to do so, something he hasn't done all that well in the past). Bowman would be the traditional middle linebacker, a la Luke Kuechly in Carolina. The leap of faith here is that Bowman will return to full strength after his second major lower-leg injury in 2 1/2 years. Who would play the 'Will,' weak-side position, which usually calls for a lighter, more athletic linebacker who can run to the ball and make plays in space? The 49ers could re-sign Ray-Ray Armstrong, who is scheduled for free agency in March. Or they could draft one. Michigan's Jabrill Peppers likely will be viewed as a safety at the NFL level because of his smaller stature (He'll likely measure 5-11, 210 pounds or so at the combine), but the Wolverines are using the aggressive, playmaker as a linebacker this season. The 49ers also could convert one of their bigger-bodied safeties (see below).
Cornerbacks: Tramaine Brock, Rashard Robinson
Notes: The 49ers should not have to worry about the spot for years. Tramaine Brock, Jimmie Ward, Rashard Robinson, Keith Reaser, Dontae Johnson, Will Redmond and JaCorey Shepherd are signed for next season.
Safeties: SS Eric Reid, FS Jimmie Ward
Notes: The question at this position is whether Ward, perhaps the team's most gifted defensive player, is best at cornerback or free safety. He started at cornerback Sunday and showed off his play-making ability against the Cardinals with four pass break-ups and seven tackles. But would that ability be better utilized at safety? And would pairing Ward with his old high-school teammate, Jaquiski Tartt, give the 49ers a faster, harder-hitting and more dynamic duo than they have now? Eric Reid, a starter since his rookie season in 2013, has played along the line of scrimmage more this season than he has in the past. Could he convert into a Will linebacker the way Thomas Davis did with the Panthers? Or maybe the safety pairing should be Ward and Reid and the team should think about using Tartt as its 'Will' linebacker.