The San Francisco 49ers have fielded an effective, sometimes dominant defensive line recently, even without factoring outside linebacker Aldon Smith into the line equation.

That's why it was shocking to see ESPN's NFL scout, Matt Williamson, rank the 49ers' defensive line fourth among those in the NFC West.

Matt Williamson Ranks West by Position

The No. 4 ranking could be misleading, however. Williamson explained why in kicking off the latest conversation in our series ranking NFC West teams at each position.

Williamson: I could make an argument to put these defensive lines in almost any order.

Sando: So, you're not necessarily downgrading Justin Smith and the rest of that 49ers line.

Williamson: I still think Smith is the best defensive lineman in the division and that is really saying something. But I wonder if his best days were in 2011. Those were very good days. He was the best defensive player in the league. You wonder if he is 90 percent of his best days, which is still a great player and the best defensive lineman in the division, but he might not be quite the same. I like Ray McDonald. Glenn Dorsey will be a nose tackle/McDonald type. They will move him around. He'll be a better version of Ricky Jean-Francois. That is who he is replacing, not Isaac Sopoaga.

Sando: The 49ers could have significant plans for Dorsey, although those remain a little vague.

Williamson: Dorsey was my favorite player in the '08 draft as a Warren Sapp type and a perfect fit for the scheme the Chiefs had at the time, but then everyone got fired, they turned him into a 3-4 defensive end and it was a totally wasted resource of a high pick. The 49ers will be smarter about how they use him than Kansas City was, but I don't think he is the same player because he has added weight and has been a slight bust.

The Seahawks added Cliff Avril to an already impressive group of defensive linemen. AP Photo/Scott Boehm

Sando: Looking at the division overall, I might have put the Rams ahead of the Seahawks. For Seattle, Chris Clemons is hurt, Alan Branch departed, Tony McDaniel was arguably a so-so replacement and Red Bryant is coming off a tough year. Michael Brockers looks like a star in the making for the Rams. Chris Long and Robert Quinn can easily combine for 20-plus sacks. William Hayes is in there too.

Williamson: I didn’t penalize the Seahawks in the rankings for Clemons' injury. He is still a really good player who will factor in at some point. He was really good on last viewing. Bruce Irvin will be better. Michael Bennett is a great addition. Cliff Avril is a phenomenal addition. They will put that NASCAR package out there when Clemons is healthy. Brandon Mebane is really good. I believe in Red Bryant. That is six quality defensive linemen and they can add somebody. McDaniel can hold his own. They can go eight deep with quality players and some fringe Pro Bowlers.

Sando: The depth is impressive. That is one area where I think the 49ers are lacking. They don't need as large of a rotation because Aldon Smith plays in their four-man line packages. Still, the Seahawks are stacked up front to a degree that came into clearer focus the way you spelled it out.

Williamson: They have a wide skill set, which I like, too. Irvin and Bryant are totally different players at defensive end. Irvin, Clemons, Avril and Bryant give you versatility. For the Rams, Hayes is an important part of that equation. He had seven sacks last year. Quinn and Long are questionable against the run. Hayes can be a base run defensive end. Plus, he moves inside and can be a quality rusher there.

Sando: I hadn't really thought of Long as a liability against the run.

Williamson: You can run at Long. Part of that is scheme. Sort of like in the Dwight Freeney-Robert Mathis days, they play the run on the way to the quarterback. With the Rams, a lot of it is ahead of them. I'd draft Quinn very high if I were building a team, but he is not as good as Cliff Avril right now. Brockers is going to be a total stud. I didn't love him coming out of LSU, but he far exceeded my expectations. I think he'll be a multiple Pro Bowl player.

Sando: We haven't even mentioned the Cardinals, who have, by the way, Calais Campbell -- arguably the best defensive lineman in the division at any given time. There are some unanswered questions about scheme as the team transitions to a new staff, however.

Williamson: Even though they ran a 3-4 defense under former coordinator Ray Horton, they allowed those defensive ends to penetrate. If they were to go to a 4-3, it would be great for Darnell Dockett. He could compete for being the best three-technique in the league. The old scheme hurt Dockett. He is a great player and a better player than people realize because he hasn't been used properly.

Sando: We'll have a better feel for the Cardinals' line once we learn more about how new coordinator Todd Bowles plans to use everyone. Dan Williams is a key variable, too. He was drafted as a 3-4 nose tackle, a position pretty specific to the Horton scheme.

Williamson: Williams has come along and is an above average 3-4 starting nose tackle.

Sando: The Cardinals also added Frostee Rucker and Matt Shaughnessy for depth, but their line's ranking probably hinges on whether the new scheme maximizes Dockett. There are also some questions about the outside pass rush. Some of those questions will arise again when we look at the Cardinals' linebackers.

Williamson: Overall, I don't love their depth on the line. They don't have that guy off the bench like Hayes or all those defensive ends in Seattle or even Dorsey in San Francisco.

Sando: Great discussion, Matt. The takeaway is pretty clear to me. This division should be strong along its defensive lines. Keeping a straight face while ranking the 49ers' line fourth drives home the point.