Glenn Dorsey and 3-4 questions for 49ers

The San Francisco 49ers probably are not going to overhaul their defensive scheme to accommodate newly added tackle Glenn Dorsey.

Initial reports suggest Dorsey will help fill the void created by nose tackle Isaac Sopoaga's departure to the Philadelphia Eagles. In that case, Dorsey would also provide insurance at defensive end in the 49ers' 3-4 scheme.

That could be the end of the story. But Dorsey's addition to an evolving line rotation invites a closer look at where the 49ers are headed on defense. It can serve as a launching point for a discussion I've been wanting to have for some time.

First, some background on why I think the 49ers have some decisions to make as they seek to sustain their recent success under coordinator Vic Fangio.

General manager Trent Baalke hinted at the subject when suggesting during the NFL scouting combine that the 49ers used a smaller rotation along their line for philosophical reasons, not depth reasons. In my view, the comments sounded like something a GM would say if he thought the defensive coordinator should be using a larger rotation.

Fangio has been known to favor veteran players. That is typical for coordinators running complex 3-4 schemes. Those schemes often function best with veteran players. Veteran players carry higher price tags. Higher price tags force tough personnel decisions as teams manage salary caps that aren't growing all that much from year to year.

That is where the 49ers are at right now. They knew they would have to let certain defensive veterans leave in free agency. Dashon Goldson was one of them. There has also been talk recently about how a scheme change could help the 49ers take better advantage of cheaper labor.

In some ways, the strength of the 49ers' front has allowed them to get by with a smaller rotation along the line. Last season proved they can't take for granted such an arrangement in the future.

A deeper, younger rotation on the line could be part of an evolution unless the 49ers are willing to make the tough choices associated with their current approach. The choices for 3-4 teams can include paying top dollar for a nose tackle and outside linebackers. Demand and prices for players best suited to the 3-4 has risen has more teams have adopted that scheme in recent seasons (perhaps to stay ahead of the curve, New England's Bill Belichick has gone away from the 3-4 over the past couple seasons).

Teams running 4-3 schemes still need to pay for pass-rushers, including at defensive tackle if they're fortunate enough to find one worthy of the investment. They can generally get by paying less for linebackers.

The 49ers are paying big money to defensive end Justin Smith through the 2013 season. They have invested heavily in inside linebackers NaVorro Bowman and Patrick Willis. They committed to Bowman for the long term after deciding he could provide value to them even if San Francisco went away from its current scheme. The idea was that Bowman and Willis would remain among the very best players on the defense regardless. They would be worth the money no matter what.

Again, I don't think the 49ers are suddenly going to unveil a 4-3 base defense. But they do have flexibility with their personnel. They could be headed in that direction. As Matt Williamson of Scouts Inc. noted when I reached out to him Wednesday, Smith was a 4-3 defensive end coming out of college. Ray McDonald was seen as an up-the-field lineman. The fact that Smith and McDonald have flourished in a 3-4 reflects well on them and on defensive line coach Jim Tomsula. There's precedent for Dorsey to make a transition, too.

On the other hand, Dorsey appears ideally suited for a 4-3 defense. That was the word on him as the fifth pick of the 2008 draft and that remained the word on him heading into free agency. And the 49ers do have the personnel to become more of a 4-3 team on defense should they choose to head in that direction.

"I could see McDonald as a three-technique type and maybe Dorsey as one-technique," Williamson said. "Ahmad Brooks could project as a 'SAM' linebacker pretty easily and Bowman would be great as the 'WILL'. Justin Smith could be a strong-side end, Aldon Smith could play the weak side. They do have the personnel."

To this point, San Francisco's defense under Fangio has relied upon a smaller number of players logging a higher number of snaps. San Francisco wore down on defense late last season, a factor in the team falling just short of a Super Bowl victory.

The 49ers are only getting started on implementing their offseason plan. Dorsey's arrival may or may not mean much in the bigger picture. But the comments Baalke made at the combine have lingered in my mind. They sounded significant. The subject will come up again as the 49ers navigate the draft and minicamps.

Back in 2001, the Indianapolis Colts loaded up on offensive players to support young quarterback Peyton Manning. As a result, they released veteran defensive players, putting the coordinator in a tough position. Fangio was that coordinator. Bill Polian, the GM back then, thought a simpler defensive scheme would help the team get more from a young defense. The head coach, Jim Mora, refused Polian's demand that he fire Fangio. Polian fired Mora and Fangio in response.

The 2013 49ers are not the Colts of a decade ago. Not even close. They have plenty of talent on offense and defense. They still have a very effective veteran core on defense. Their quarterback remains under contract on the cheap for another season at least, providing flexibility. Fangio just helped the 49ers get to the Super Bowl. Now is not the time to scrap what has gotten the 49ers to this point. But there are some tradeoffs to consider, at least, and the 49ers are well aware of them. I wonder to what degree the team will alter its defense with sustainability in mind.