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After a slow 1-2 start on the season, the 49ers have rebounded quite nicely with three straight victories. The 49ers currently stand second in the NFC West standings with a respectable 4-2 record.

Outside of the 31-17 win over the St. Louis Rams, their average margin of victory has been quite small. However, when you factor in the injuries this team has suffered, being two games over .500 is a victory in itself.

So, how are the 49ers winning football games with a banged-up roster?

Well, it all starts with the reserves, who have played sensational football in the absence of several key starters. We have a few who deserve praise, including cornerback Perrish Cox and rookie lineman Aaron Lynch. Even newcomer Antoine Bethea is playing at a Pro Bowl level.

However, there is one reserve who's receiving zero attention for his play.

Forget the flashy guys, here are a few reasons why nose tackle Ian Williams is playing at a high level for this undermanned 49ers defense.

Stuffing the Run

Many have forgotten, but it was Williams who won the starting nose tackle position in training camp last year. Williams beat out Glenn Dorsey for the right to start but suffered a season-ending injury in Week 2 of the 2013 season.

Dorsey took over and didn't look back.

Now, I still think a healthy Dorsey would have reclaimed his starting job this season, but it would be an interesting battle nonetheless.

Both players have different but valuable skill sets. For one, Dorsey is a far better pass-rusher than Williams. The 49ers' pass rush up the middle was very solid last season, and with Dorsey's absence, you're starting to see why this defense is struggling to apply pressure on opposing quarterbacks.

With Williams, you're getting a very stout run defender who can manhandle the point of attack. Don't believe me, just ask Justin Smith.

Matt Barrows of The Sacramento Bee relays Smith's trust in Williams' ability to stop the run up the middle. "Trust me, teams are trying to run directly at him. They’re not getting the movement on him that they want. That’s why they’re going to the edges," he said.

Smith isn't offering hyperbole—just look at the stats. The 49ers have the fifth-best rushing defense despite the absence of two All-Pro linebackers.

Underrated Pass-Rusher

As I stated before, the 49ers will miss Dorsey's pass-rushing ability up the middle. Don't fret, though: Williams is no slouch in this area.

Yes, the 49ers' pass rush has looked awful at times in the first six games, but I wouldn't necessarily blame Williams for the struggles.

A traditional nose tackle like Williams isn't supposed to be a great pass-rusher. However, his short-area quickness and agility give him a unique skill set.

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He has the strength to provide a great bull rush, while also possessing enough quickness to get after the quarterback. Williams almost always has the advantage over slower-footed interior linemen.

The 49ers don't give Williams a chance to show off his pass-rushing ability very often, but when they let the big man loose, opposing quarterbacks should watch out.

Pursuit and Athleticism

This is what makes Williams a potentially special player. He's played at an All-Pro level through the first six weeks, but if he continues to improve, we could be talking about Williams as a potential centerpiece on this defensive line.

Pro Football Focus seems to agree with me, as the play of William's has caught the eye of many around the league. Williams was chosen as the site's starting nose tackle in its first-quarter All-Star team.

"What’s not to like about Williams? Maybe he could do with more playing time but lining up as a more traditional nose tackle gets him extra marks. He’s been a quiet revelation in San Francisco," wrote PFF's Khaled Elsayed.

"He’s strong at the point and he’s fast at pursuing. That’s what makes him a really good nose,” Smith told Barrows.

When you have an athletic nose tackle, it gives your defense a versatile piece to move around. This is perfect for defensive coordinator Vic Fangio, who employs a rather creative 3-4 defense in which players are asked to play multiple positions along the defensive line.

If Dorsey can return this season, the 49ers will have a tough choice to make. Do you go with Dorsey or stick with the hot hand in Williams?

I'm sure the answer is not clear at the moment, but if Williams can keep up this level of play, the 49ers will have their starting nose tackle for the foreseeable future.